Perfusion and oxygenation measurement

ABSTRACT

The present disclosure provides methods and apparatus for evaluating the flow of blood in damaged or healing tissue. The present disclosure also provides methods of identifying a patient at the onset of risk of pressure ulcer or at risk of the onset of pressure ulcer, and treating the patient with anatomy-specific clinical intervention selected based on perfusion or blood oxygenation values, or a combination thereof. The present disclosure also provides methods of stratifying groups of patients based on risk of wound development and methods of reducing incidence of tissue damage in a care facility. The present disclosure also provides methods to analyze trends of perfusion or oxygenation measurements to detect tissue damage before it is visible, and methods to compare bisymmetric perfusion values to identify damaged tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication 62/698,684 filed Jul. 16, 2018, and U.S. ProvisionalApplication 62/849,700 filed May 17, 2019, each of which is hereinincorporated by reference in its entirety.

FIELD

The present disclosure provides methods and apparatus for evaluating theflow of blood in damaged or healing tissue. The present disclosure alsoprovides methods of identifying a patient at the onset of risk ofpressure ulcer or at risk of the onset of pressure ulcer, and treatingthe patient with anatomy-specific clinical intervention selected basedon measurements of blood perfusion or oxygenation values, or acombination thereof. The present disclosure also provides methods ofstratifying groups of patients based on the risk of wound development,and methods of reducing the incidence or severity of tissue damage inpatients admitted to a care facility. The present disclosure alsoprovides apparatuses and computer readable media for measuring bloodperfusion in patients to identify damaged tissue for anatomy-specificclinical intervention, and methods for identifying damaged tissue. Thepresent disclosure also provides methods of detecting tissue damagebefore the tissue damage is visible on a patient's skin.

BACKGROUND

The skin is the largest organ in the human body. It is readily exposedto different kinds of damages and injuries. Skin damage and injury mayresult when the skin and its surrounding tissues are unable toredistribute external pressure and mechanical forces, ulcers may beformed. Prolonged continuous exposure to even modest pressure, such asthe pressure created by the body weight of a supine patient on theirposterior skin surfaces, may lead to a pressure ulcer. In the presenceof other damage, such as the neuropathy and peripheral tissue weakeningthat can be induced by diabetes, even periodic exposure to moderatelevels of pressure and stress may lead to an ulcer, for example a footulcer.

Pressure ulcers are developed by approximately 2.5 million people a yearin the United States and an equivalent number in the European Union. Inlong-term and critical-care settings, up to 25% of elderly and immobilepatients develop pressure ulcers. Approximately 60,000 U.S. patients dieper year due to infection and other complications from pressure ulcers.

Most pressure ulcers occur over bony prominences, where there is lesstissue for compression and the pressure gradient within the vascularnetwork is altered. Pressure ulcers are categorized in one of sixstages, ranging from the earliest stage currently recognized, in whichthe skin remains intact but may appear red over a bony prominence (Stage1), to a stage where tissue is broken and bone, tendon or muscle isexposed (Stage 4), to deep tissue pressure injury showing non-blanchabledeep red, maroon, or purple discoloration, and to a stage where there isobscured full-thickness skin and tissue loss (unstageable). Detectingpressure ulcers before the skin breaks and treating them to avoidprogression to later stages is a goal of policy makers and careproviders in major economies. Most pressure ulcers are preventable, andif identified before the first stage of ulceration, deterioration of theunderlying tissue can be halted.

Detecting tissue damage before the skin breaks and intervening with theappropriate therapy to avoid further deterioration of the underlyingtissue is desirable not only for the patient but society. The averagecost of treating pressure-induced damage at the earliest visible sign (aStage 1 ulcer) is only $2,000 but this rises to $129,000 when the ulceris deep enough to expose muscle or bone (a Stage 4 ulcer). See, e.g.,Brem, H. et al. (2010). High Cost of Stave IV Pressure Ulcers. Am. J.Surg. October; 200(4):473-477. Currently, patients normally receiveuniversal prevention of pressure ulcers, meaning that the preventiondoes not target to any particular anatomical sites. Patients onlyreceive a targeted, localized, treatment of ulcer after the pressureulcer is developed to the point that it can be identified by a visualassessment. The current standard to detect pressure ulcers is by visualinspection, which is subjective, unreliable, untimely, and lacksspecificity. See, e.g., Pancorbo-Hidalgo P. et al. (2006). Riskassessment scales for pressure ulcer prevention: a systematic review.Journal of Advanced Nursing, 54, 94-110; Garcia-Fernandez, F. P. (2014).Predictive Capacity of Risk Assessment Scales and Clinical Judgment forPressure Ulcers: A Meta-analysis. Journal of wound, Ostomy andContinence Nursing 41, 24-34. Therefore, even when a patient isexperiencing inflammation of the skin, a precursor of ulcer development,he or she would not be receiving a targeted, localized treatment for thedeveloping ulcer. Instead, the inflammation would continue to developinto a full-blown ulcer.

Skin damage and injury may also result from certain types of surgicalprocedures, for example reconstructive surgery involving skin flaps,will sever blood vessels in or around the area of surgery. Healing ofdamaged or separated tissue is dependent upon re-establishment ofadequate blood flow throughout the damaged area. Determining whether anarea of tissue is healing, i.e. that blood flow through the tissue isincreasing to a normal level, is difficult to do via visual inspection.Existing equipment can measure certain attributes, such as theoxygenation level of the blood, that are at best indirect measures ofblood flow.

Fluorescein has been used for over 40 years to clinically assess flapvascularity. Fluorescein will emit a yellow-green (510-600 nm)fluorescence when excited by ultraviolet (UV) light. Tissue with goodblood flow will appear bright yellow while areas without blood flowappear dark blue. Fluorescein is usually given in a bolus injection of500-1000 mg. After waiting 20-30 min, the tissue can be assessed with aUV lamp. This method takes 30 minutes to implement and can only be usedevery 8 hours.

Near infrared spectroscopy (NIRS) is used to determine the ratio ofoxygenated to de-oxygenated hemoglobin by proving specific wavelengthsof light (760 nm and 830 nm) and measuring the amount of reflected ortransmitted light. There are devices available now that provide imagesshowing the local oxygenation of the skin surface. While this is animportant piece of clinical information, it does not reveal the actualperfusion level of the tissue nor does it separate the condition of thesurface tissue from the condition of the deeper layers of the tissue.

Two types of Doppler instruments are currently in clinical use. Thefirst is the ultrasound Doppler, which senses the phase shift ofreflected sound to measure the velocity of moving elements, presumed tobe the red blood cells in a blood vessel. The second is the laserDoppler, which senses the phase shift of reflected light to detect thevelocity of the red blood cells. These methods are limited to assessingthe blood flow in the larger blood vessels and cannot assess perfusionin the finer arterioles and capillaries.

SUMMARY

Systematic methods using non-invasive, objective measurements toidentify the onset of the risk of pressure ulcer before visible skindamages, followed by administering individualized intervention atspecific anatomy are provided. Systematic methods using non-invasive,objective measurements to identify the onset of a pressure ulcer beforevisible skin damages, followed by administering individualizedintervention at specific anatomy are also provided. Methods formonitoring progression of wound healing and consistency of interventioncompliance are further provided.

In an aspect, the present disclosure provides for, and includes, anapparatus for assessing perfusion of blood in tissue below a patient'sskin. The apparatus includes an emitter configured to emit light at afirst wavelength and a second wavelength when activated, a firstreceiver configured to measure a first intensity of received light atthe first wavelength and a second intensity of received light at thesecond wavelength and provide a first signal comprising informationabout the first and second intensities of the received light, asubstrate coupled to the emitter and the first receiver and configuredsuch that the emitter and first receiver can be placed in simultaneouscontact with the patient's skin, and a processor coupled to the firstreceiver. The processor is configured to receive the first signal,determine a first summation value of the first and second intensities ofthe received light, and determine a level of perfusion of the tissuefrom the first summation value.

In an aspect, the present disclosure provides for, and includes, amethod of assessing perfusion of blood in tissue below a patient's skin.The method includes the step of emitting light into the patient's skinat a first location on the patient's skin. The light has a firstwavelength and a second wavelength. The method also includes the stepsof receiving a portion of the emitted light that has been reflected fromthe tissue, measuring a first intensity of received light at the firstwavelength and a second intensity of received light at the secondwavelength, determining a first summation value of the first and secondintensities of the received light.

In an aspect, the present disclosure provides for, and includes, anapparatus for assessing perfusion of blood in tissue below a patient'sskin. The apparatus includes an emitter configured to selectably emitlight at a first wavelength or emit light at a second wavelength, acamera configured to form a first image of reflected light at the firstwavelength and a second image of reflected light at the secondwavelength, and a substrate coupled to the emitter and the camera. Thesubstrate can be placed such that the light emitted by the emitterilluminates a portion of the skin of the patient that is within a fieldof view of the camera. The apparatus also includes a display and aprocessor that is coupled to the camera and the display and configuredto receive the first and second images, form a third image that is asummation of the first and second images, and provide the third image onthe display.

In an aspect, the present disclosure provides for, and includes, amethod of reducing the incidence of wound development in patientsadmitted to a care facility, the method comprising the steps of:evaluating a patient for a risk of tissue damage upon admission to thecare facility, where the evaluating step comprises making a firstplurality of perfusion measurements in the patient at one or more bodylocations at risk of wound development, calculating a first delta valuefrom a portion of the first plurality of perfusion measurements,determining whether the first delta value exceeds a first threshold,administering a first intervention of level-0 if the first delta valuedoes not exceed the first threshold, and administering an interventionof level-N if the first delta value exceeds the first threshold, where Nis an integer and N has a value of 1 or greater. In one aspect, one ormore body locations at risk of wound development are selected from thegroup consisting of a sternum, a sacrum, a heel, a scapula, an elbow, anear, and other fleshy tissues over a bony prominence of a patient. In anaspect, one or more body locations at risk of wound development compriseone or more anatomical sites in long-term contact with a medical device,and are selected from the group consisting of a cheek, a nose, a chest,a stomach, and a lower abdomen area.

In an aspect, the present disclosure provides for, and includes, amethod of reducing the incidence of wound development in patientsadmitted to a care facility, the method comprising the steps of:evaluating a patient for a risk of tissue damage upon admission to thecare facility, where the evaluating step comprises making a firstplurality of SpO₂ measurements in the patient at one or more bodylocations at risk of wound development, determining whether any of thefirst plurality of SpO₂ measurements is below a first threshold,administering a first intervention of level-0 if the first plurality ofSpO₂ measurements are above or equal to the first threshold, andadministering an intervention of level-N if any of the first pluralityof SpO₂ measurements is below a first threshold, where N is an integerand N has a value of 1 or greater. In one aspect, one or more bodylocations at risk of wound development are selected from the groupconsisting of a sternum, a sacrum, a heel, a scapula, an elbow, an ear,and other fleshy tissues over a bony prominence of a patient. In anaspect, one or more body locations at risk of wound development compriseone or more anatomical sites in long-term contact with a medical device,and are selected from the group consisting of a cheek, a nose, a chest,a stomach, and a lower abdomen area.

In an aspect, the present disclosure provides for, and includes, amethod of stratifying groups of patients in a care facility based on therisk of wound development, the method comprising the steps of: making aplurality of perfusion measurements in each of the patients at one ormore body locations selected for monitoring, calculating a delta valuefrom a portion of the plurality of perfusion measurements for each ofthe patients, determining whether each delta value exceeds any values ina set of threshold values corresponding to N care levels and assigning acare level to each of the patients, and rearranging the group ofpatients based on each of the patient's assigned care levels. In oneaspect, one or more body locations for monitoring are selected from thegroup consisting of a sternum, a sacrum, a heel, a scapula, an elbow, anear, and other fleshy tissues over a bony prominence of a patient. In anaspect, one or more body locations for monitoring comprise one or moreanatomical sites in long-term contact with a medical device, and areselected from the group consisting of a cheek, a nose, a chest, astomach, and a lower abdomen area.

In an aspect, the present disclosure provides for, and includes, amethod of stratifying groups of patients in a care facility based on therisk of wound development, the method comprising the steps of: making aplurality of SpO₂ measurements in each of the patients at one or morebody locations selected for monitoring, determining whether each of theplurality of SpO₂ measurements is below any values in a set of thresholdvalues corresponding to N care levels and assigning a care level to eachof the patients, and rearranging the group of patients based on each ofthe patient's assigned care levels. In one aspect, one or more bodylocations for monitoring are selected from the group consisting of asternum, a sacrum, a heel, a scapula, an elbow, an ear, and other fleshytissues over a bony prominence of a patient. In an aspect, one or morebody locations for monitoring comprise one or more anatomical sites inlong-term contact with a medical device, and are selected from the groupconsisting of a cheek, a nose, a chest, a stomach, and a lower abdomenarea.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and providing an appropriate level of care to apatient based on a plurality of blood perfusion measurements of tissuebelow a patient's skin. In an aspect, a patient is provided withanatomy-specific intervention based on a plurality of blood perfusionmeasurements of tissue below a patient's skin. In an aspect, a patientis provided with increasingly intensive therapeutic interventions basedon changes in perfusion measurements. In an aspect, a patient is givenless intensive therapeutic interventions based on changes in perfusionmeasurements.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and providing an appropriate level of care to apatient based on a plurality of blood oxygenation (SpO₂) measurements oftissue below a patient's skin. In an aspect, a patient is provided withanatomy-specific intervention based on a plurality of SpO₂ measurementsof tissue below a patient's skin. In an aspect, a patient is providedwith increasingly intensive therapeutic interventions based on changesin SpO₂ measurements. In an aspect, a patient is given less intensivetherapeutic interventions based on changes in SpO₂ measurements.

In an aspect, the present disclosure provides for, and includes, amethod of assessing a patient, the method comprising the steps of:performing initial blood perfusion measurements of a location of thebody selected for monitoring, and assigning the patient to a riskcategory selected from a group comprising a plurality of riskcategories, where the assigning is based partially on the initialperfusion measurements of the body location.

In an aspect, the present disclosure provides for, and includes, amethod of assessing a patient, the method comprising the steps of:performing initial SpO₂ measurements of a location of the body selectedfor monitoring, and assigning the patient to a risk category selectedfrom a group comprising a plurality of risk categories, where theassigning is based partially on the initial SpO₂ measurements of thebody location.

In an aspect, the present disclosure provides for, and includes, amethod of managing care of a patient, the method comprising the stepsof: performing an initial evaluation of the patient and taking aninitial set of perfusion measurements at all body locations selected formonitoring upon admission to a care facility, calculating an initialdelta value for each body location selected for monitoring, determiningthat a patient's measurements are abnormal and setting an interventionlevel to N=1 if any initial delta value is greater than or equal to afirst threshold, implementing a level-N intervention for each bodylocation having a delta value that is greater than or equal to the firstthreshold, and performing blood perfusion measurements of all bodylocations at a level-N frequency and calculating new delta values. Inone aspect, one or more body locations for monitoring are selected fromthe group consisting of a sternum, a sacrum, a heel, a scapula, anelbow, an ear, and other fleshy tissues over a bony prominence of apatient. In an aspect, one or more body locations for monitoringcomprise one or more anatomical sites in long-term contact with amedical device, and are selected from the group consisting of a cheek, anose, a chest, a stomach, and a lower abdomen area.

In an aspect, the present disclosure provides for, and includes, amethod of managing care of a patient, the method comprising the stepsof: performing an initial evaluation of the patient and taking aninitial set of SpO₂ measurements at all body locations selected formonitoring upon admission to a care facility, determining that apatient's measurements are abnormal and setting an intervention level toN=1 if any initial SpO₂ measurements is less than a first threshold,implementing a level-N intervention for each body location having a SpO₂measurement that is less than the first threshold, and performing SpO₂measurements of all body locations at a level-N frequency.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient at risk of tissue damage,the method comprising the steps of: evaluating a patient for a risk oftissue damage upon admission to a care facility, where the evaluatingstep comprises making a first plurality of perfusion measurements in thepatient, calculating a first delta value from a portion of the firstplurality of perfusion measurements, determining whether the first deltavalue exceeds a first threshold, administering a first intervention oflevel-0 if the first delta value does not exceed the first threshold,and administering a first intervention of level-N if the first deltavalue exceeds the first threshold, where N is an integer and N has avalue of 1 or greater. In a further aspect, the present disclosureprovides for, and includes, making a second plurality of perfusionmeasurements in the patient at a first pre-determined frequencycorresponding to the administered intervention level, calculating asecond delta value from a portion of the second plurality of perfusionmeasurements, determining whether the second delta value exceeds asecond threshold, continuing to administer the first intervention if thesecond delta value does not exceed the second threshold, continuing tomake a plurality of perfusion measurements at the first pre-determinedfrequency if the second delta value does not exceed the secondthreshold, administering a second intervention of level-M if the seconddelta value exceeds the second threshold, where M is an integer and M isgreater than N, and making a plurality of perfusion measurements at asecond pre-determined frequency corresponding to level-M if the seconddelta value exceeds the second threshold. In yet a further aspect, thepresent disclosure provides for, and includes, determining whether thesecond delta value is less than a third threshold, administering alevel-(N−1) intervention if the second delta value is less than thethird threshold and if the first intervention is not of level-0, andmaking a plurality of perfusion measurements at a pre-determinedfrequency corresponding to level-(N−1) if the second delta value is lessthan the third threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient at risk of tissue damage,the method comprising the steps of: evaluating a patient for a risk oftissue damage upon admission to a care facility, where the evaluatingstep comprises making a first plurality of SpO₂ measurements in thepatient, determining whether any of the first plurality of SpO₂measurements is below a first threshold, administering a firstintervention of level-0 if the first plurality of SpO₂ measurements isgreater than or equal to the first threshold, and administering a firstintervention of level-N if any of the first plurality of SpO₂measurements is below the first threshold, where N is an integer and Nhas a value of 1 or greater. In a further aspect, the present disclosureprovides for, and includes, making a second plurality of SpO₂measurements in the patient at a first pre-determined frequencycorresponding to the administered intervention level, calculating a timedelta value based on the differences between the first plurality and thesecond plurality of SpO₂ measurements, determining whether the timedelta value is a decrease exceeding a second threshold, continuing toadminister the first intervention if the time delta value does notexceed the second threshold, continuing to make a plurality of perfusionmeasurements at the first pre-determined frequency if the time deltavalue does not exceed the second threshold, administering a secondintervention of level-M if the time delta value is a decrease exceedingthe second threshold, where M is an integer and M is greater than N, andmaking a plurality of SpO₂ measurements at a second pre-determinedfrequency corresponding to level-M if the time delta value is a decreaseexceeding the second threshold. In yet a further aspect, the presentdisclosure provides for, and includes, determining whether the timedelta value is an increase exceeding a third threshold, administering alevel-(N−1) intervention if the time delta value is an increaseexceeding the third threshold and if the first intervention is not oflevel-0, and making a plurality of SpO₂ measurements at a pre-determinedfrequency corresponding to level-(N−1) if the time delta value is anincrease exceeding the third threshold.

In an aspect, the present disclosure provides for, and includes, amethod of slowing the progression of skin and tissue damage in a patientin need thereof, the method comprising the steps of: identifying acurrent intervention of level-K received by the patient, making aplurality of perfusion measurements in the patient, calculating a deltavalue from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a first threshold,continuing to administer the current intervention if the delta valuedoes not exceed the first threshold, continuing to make a plurality ofperfusion measurements at a pre-determined frequency corresponding tolevel-K if the delta value does not exceed the first threshold,administering a new intervention of level-N if the delta value exceedsthe first threshold, where N has a value greater than K, and making aplurality of perfusion measurements at a pre-determined frequencycorresponding to level-N if the delta value exceeds the first threshold.In a further aspect, the present disclosure provides for, and includes,determining whether the delta value is less than a second threshold,administering a level-L intervention if the delta value is less than thesecond threshold, where L has a non-negative value less than K, andmaking a plurality of perfusion measurements at a pre-determinedfrequency corresponding to level-L if the delta value is less than thesecond threshold.

In an aspect, the present disclosure provides for, and includes, amethod of slowing the progression of skin and tissue damage in a patientin need thereof, the method comprising the steps of: identifying acurrent intervention of level-K received by the patient, making aplurality of SpO₂ measurements in the patient, determining whether anyof the a plurality of SpO₂ measurements exceeds a first threshold,continuing to administer the current intervention if the plurality ofSpO₂ measurements are within a threshold range corresponding to level-K,continuing to make a plurality of perfusion measurements at apre-determined frequency corresponding to level-K if the delta value arewithin a threshold range corresponding to level-K, administering a newintervention of level-N if any of the plurality of SpO₂ measurements isbelow the first threshold range, where N has a value greater than K, andmaking a plurality of perfusion measurements at a pre-determinedfrequency corresponding to level-N if any of the plurality of SpO₂measurements is below the first threshold range. In a further aspect,the present disclosure provides for, and includes, determining whetherany of the plurality of SpO₂ measurements is above the threshold rangecorresponding to level-K, administering a level-L intervention if any ofthe plurality of SpO₂ measurements is above the threshold rangecorresponding to level-K, where L has a non-negative value less than K,and making a plurality of SpO₂ measurements at a pre-determinedfrequency corresponding to level-L if any of the plurality of SpO₂measurements is above the threshold range corresponding to level-K.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a barrier cream to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every two hours if any of the pluralityof SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's heel, the method comprisingthe steps of: making a plurality of perfusion measurements at thepatient's heel, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'sheel if the delta value exceeds the threshold, and making a plurality ofperfusion measurements every hour if the delta value exceeds thethreshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's heel, the method comprisingthe steps of: making a plurality of SpO₂ measurements at the patient'sheel, determining whether any of the plurality of SpO₂ measurements isbelow a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'sheel if any of the plurality of SpO₂ measurements is below thethreshold, and making a plurality of SpO₂ measurements every hour if anyof the plurality of SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a topical cream to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery half an hour if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every half an hour if any of theplurality of SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aheel boot to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a heel boot to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery half an hour if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aheel boot to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a heel boot to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every half an hour if any of theplurality of SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's sacrum, the method comprising the stepsof: making a plurality of perfusion measurements at the patient'ssacrum, calculating a delta value from a portion of the plurality ofperfusion measurements, determining whether the delta value exceeds athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's sacrum if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every six hours if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's sacrum, the method comprising the stepsof: making a plurality of SpO₂ measurements at the patient's sacrum,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's sacrum if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every six hours if any of the pluralityof SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's sacrum, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's sacrum, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'ssacrum if the delta value exceeds the threshold, and making a pluralityof perfusion measurements every four hours if the delta value exceedsthe threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's sacrum, the methodcomprising the steps of: making a plurality of SpO₂ measurements at thepatient's sacrum, determining whether any of the plurality of SpO₂measurements is below a threshold corresponding to level N, where N isgreater than or equal to 2, administering a neuro-muscular stimulationto the patient's sacrum if any of the plurality of SpO₂ measurements isbelow the threshold, and making a plurality of SpO₂ measurements everyfour hours if any of the plurality of SpO₂ measurements is below thethreshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's sacrum, the method comprising the stepsof: making a plurality of perfusion measurements at the patient'ssacrum, calculating a delta value from a portion of the plurality ofperfusion measurements, determining whether the delta value exceeds athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's sacrum if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's sacrum, the method comprising the stepsof: making a plurality of SpO₂ measurements at the patient's sacrum,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's sacrum if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every two hours if any of the pluralityof SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application oftherapeutic ultrasound, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering therapeutic ultrasound to the anatomic site if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.In an aspect, an anatomical site is selected from the group consistingof a sternum, a sacrum, a heel, a scapula, an elbow, an ear, and otherfleshy tissues over a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application oftherapeutic ultrasound, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering therapeutic ultrasound to the anatomic site if any ofthe plurality of SpO₂ measurements is below the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application ofshockwave therapy, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering shockwave therapy to the anatomic site if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient. In one aspect, shockwave therapy isprovided via electromagnetic pulse or pressurized air.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application ofshockwave therapy, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering shockwave therapy to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient. In one aspect, shockwave therapy isprovided via electromagnetic pulse or pressurized air.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of a30-degree wedge, the method comprising the steps of: making a pluralityof perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a 30-degree wedge to the anatomic site if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of a30-degree wedge, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a 30-degree wedge to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of acomposite dressing, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a composite dressing to the anatomic site if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.In an aspect, an anatomical site is selected from the group consistingof a sternum, a sacrum, a heel, a scapula, an elbow, an ear, and otherfleshy tissues over a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of acomposite dressing, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a composite dressing to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of a hybridmattress, the method comprising the steps of: making a plurality ofperfusion measurements at an anatomic site of the patient, calculating adelta value from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a threshold corresponding tolevel N, where N is greater than or equal to 2, providing a hybridmattress to support the patient if the delta value exceeds thethreshold, and making a plurality of perfusion measurements every twohours if the delta value exceeds the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of ahybrid mattress, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,providing a hybrid mattress to support the patient if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of a dynamicmattress, the method comprising the steps of: making a plurality ofperfusion measurements at an anatomic site of the patient, calculating adelta value from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a threshold corresponding tolevel N, where N is greater than or equal to 2, providing a dynamicmattress to support the patient if the delta value exceeds thethreshold, and making a plurality of perfusion measurements every twohours if the delta value exceeds the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of adynamic mattress, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,providing a dynamic mattress to support the patient if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, anapparatus for identifying damaged tissue, the apparatus comprising: aperfusion measurement device of the present disclosure for assessingperfusion of blood in tissue below a patient's skin; a processorelectronically coupled to the perfusion measurement device andconfigured to receive the information from the perfusion measurementdevice and convert the information regarding the measured reflectedlight into a perfusion value; and a non-transitory computer-readablemedium electronically coupled to the processor and comprisinginstructions stored thereon that, when executed on the processor,perform the step of: determining a difference between a first perfusionvalue corresponding to a measurement taken at a first location on thepatient's skin and a second perfusion value corresponding to ameasurement taken at a second location on the patient's skin, where thesecond location is bisymmetric relative to the first location.

In an aspect, an apparatus for identifying damaged tissue is provided bythe present disclosure, the apparatus comprising: a substrate configuredto be placed against a surface of a patient's skin; a perfusionmeasurement device of the present disclosure for assessing perfusion ofblood in tissue below a patient's skin, comprising a plurality ofemitters and a plurality of receivers that are disposed on the substratea respective plurality of positions; a processor electronically coupledto the perfusion measurement device and configured to receiveinformation regarding the reflected light measurements from theplurality of receivers and convert the information into a respectiveplurality of perfusion values; and a non-transitory computer-readablemedium electronically coupled to the processor and comprisinginstructions stored thereon that, when executed on the processor,perform the steps of: identifying from the plurality of perfusion valuesa first receiver and a second receiver that are located at first andsecond positions that are bisymmetric to one another with respect to thepatient's skin, and comparing a first perfusion value that is associatedwith the first receiver with a second perfusion value that is associatedwith the second receiver.

In an aspect, an apparatus for identifying damaged tissue is provided bythe present disclosure, the apparatus comprising: an apparatus body; atleast one emitter; a first receiver and a second receiver, where the tworeceivers are disposed on the apparatus body to allow simultaneouspositioning of the first receiver on a first location on a patient'sskin and the second receiver on a second location bisymmetric relativeto the first location; a processor electronically coupled to the tworeceivers and configured to receive a first reflected light measurementfrom a first location and a second reflected light measurement from asecond location, and to convert the first reflected light measurement toa first perfusion value and the second reflected light measurement intoa second perfusion value; a non-transitory computer-readable mediumelectronically coupled to the processor and contains instructions that,when executed on the processor, perform the step of determining adifference between the first perfusion value and the second perfusionvalue.

In an aspect, a method for identifying damaged tissue is provided by thepresent disclosure, the method comprising: obtaining a first perfusionvalue from a first location on a patient's skin; obtaining a secondperfusion value from a second location that is bisymmetric relative tothe first location; determining a difference between a first perfusionvalue and a second perfusion value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of perfusion values at a singlelocation at incremental times, calculating a slope between the latestperfusion value and the immediately prior perfusion value, comparingthis slope to a threshold value, and determining that there is tissuedamage if the slope exceeds the threshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of perfusion values at aplurality of locations at incremental times, calculating a delta valuefor the plurality of perfusion values for each time, calculating a slopebetween the latest delta value and the immediately prior delta value,comparing this slope to a threshold value, and determining that there istissue damage if the slope exceeds the threshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of perfusion values at aplurality of locations at incremental times, calculating a delta valuefor the plurality of perfusion values for each time, calculating aderivative between the latest delta value and the immediately priordelta value, comparing this derivative to a threshold value, anddetermining that there is tissue damage if the derivative exceeds thethreshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of perfusion values at a singlelocation at each of a plurality of incremental times, calculating aperfusion delta value for each incremental time, fitting a curve to apredetermined number of the most-recent perfusion delta values,calculating a curvature of the fitted curve, comparing this curvature toa threshold value, and determining that there is tissue damage if thecurvature exceeds the threshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of SpO₂ values at a singlelocation at incremental times, calculating a slope between the latestSpO₂ value and the immediately prior SpO₂ value, comparing this slope toa threshold value, and determining that there is tissue damage if theslope exceeds the threshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of SpO₂ values at a singlelocation at incremental times, calculating a derivative between thelatest SpO₂ value and the immediately prior SpO₂ value, comparing thisderivative to a threshold value, and determining that there is tissuedamage if the derivative exceeds the threshold value.

In an aspect, the present disclosure provides for, and includes, amethod of detecting tissue damage before it is visible on a patient'sskin, comprising: measuring a plurality of SpO₂ values at a singlelocation at each of a plurality of incremental times, calculating anaverage value for each incremental time, fitting a curve to apredetermined number of the most-recent SpO₂ average values, calculatinga curvature of the fitted curve, comparing this curvature to a thresholdvalue, and determining that there is tissue damage if the curvatureexceeds the threshold value.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure are herein described, by way of example only,with reference to the accompanying drawings. With specific reference nowto the drawings in detail, it is stressed that the particulars shown areby way of example and are for purposes of illustrative discussion ofaspects of the disclosure. In this regard, the description and thedrawings, considered alone and together, make apparent to those skilledin the art how aspects of the disclosure may be practiced.

FIG. 1 depicts the tissue around a burn.

FIGS. 2A and 2B depict a skin flap created as part of breastreconstruction surgery.

FIG. 3 is a representative plot of the absorption spectrum of oxygenatedand de-oxygenated hemoglobin.

FIG. 4 depicts a block diagram of an example perfusion measurementdevice, in accordance with the present disclosure.

FIG. 5 depicts an exemplary configuration of a perfusion measurementdevice, in accordance with the present disclosure.

FIG. 6 depicts a cross-section of tissue showing how emitted light isreflected by the tissue, in accordance with the present disclosure.

FIG. 7 depicts the emitted and detected signals of an example system, inaccordance with the present disclosure.

FIG. 8 depicts the paths of reflected light with a wide-angle source, inaccordance with the present disclosure.

FIG. 9 depicts the emitted signal and detected signals of a systemsimilar to that of FIG. 8 , in accordance with the present disclosure.

FIGS. 10A and 10B depict the detected signals of light reflected fromoxygenated and de-oxygenated hemoglobin, in accordance with the presentdisclosure.

FIGS. 11A and 11B depict the detected signals of light reflected fromoxygenated and de-oxygenated hemoglobin along a line across a wound, inaccordance with the present disclosure.

FIG. 11C is a plot of comparative points of the curves of FIGS. 11A and11B, in accordance with the present disclosure.

FIG. 11D depict an example wound and an exemplary map of the line ofmeasurements of the plot of FIG. 11C, in accordance with the presentdisclosure system.

FIG. 11E depicts an example plot of perfusion summation values takenacross a different wound, in accordance with the present disclosure.

FIGS. 12A, 12B, 12C, and 12D depict examples of the disclosedapparatuses, in accordance with the present disclosure.

FIG. 13 is a flowchart of an exemplary method of perfusion measurement,in accordance with the present disclosure.

FIG. 14 depicts an example of an overall process for selecting atreatment for a wound based on perfusion measurements, where the processcovers the time period from admission of a patient to a care facilityuntil discharge of the patient from the care facility, in accordancewith the present disclosure.

FIG. 15 is an illustration of a process for selecting a level ofintervention and monitoring based on the amount by which a delta valuederived from perfusion measurements exceeds a threshold value inaccordance with the present disclosure.

FIG. 16 is an example of a workflow guidance matrix where the currentlevel of intervention and the new delta value are used to select the newlevel of intervention in accordance with the present disclosure.

FIG. 17 is an example plot of a delta value change over time for asingle patient at a single wound location in accordance with the presentdisclosure.

FIGS. 18A and 18B are examples of methods of mapping areas of tissuedamage in accordance with the present disclosure.

FIG. 19A is an example of a currently recommended treatment decisionpathway for preventing pressure ulcers in hospital patients using acombination of risk assessment and visual assessment.

FIG. 19B is an example of a current augmented treatment decision pathwayfor preventing pressure ulcers as currently implemented at some healthcare facilities.

FIG. 20 is an example flowchart of how an apparatus for assessingperfusion of blood in tissue below a patient's skin may be used in astand-alone process to prevent pressure ulcers, in accordance with thepresent disclosure.

FIG. 21 is an example flowchart of how an apparatus for assessingperfusion of blood in tissue below a patient's skin may be used as anadjunct to further improve the augmented treatment decision pathway ofFIG. 19B, in accordance with the present disclosure.

FIG. 22A provides an example of a pair of bisymmetric locations on asacral region according to the present disclosure.

FIG. 22B provides an example of a pair of bisymmetric locations on thebottom side of both feet according to the present disclosure.

FIG. 22C provides an example of a pair of bisymmetric locations on thelateral sides and soles of both feet according to the presentdisclosure.

FIG. 23A illustrates locations on the left and right feet for perfusionmeasurements according to the present disclosure.

FIG. 23B is a plot of perfusion values associated with known relativelocations for identifying bisymmetric locations according to the presentdisclosure.

FIG. 24 depicts an integrated system for measurement, evaluation,storage, and transfer of perfusion values, according to the presentdisclosure.

FIG. 25 depicts perfusion values over time for patients who are at riskof developing pressure ulcers, in accordance with the presentdisclosure.

FIG. 26 depicts perfusion delta values over time for patients thatdevelop pressure ulcers, in accordance with the present disclosure.

FIG. 27 depicts illustrative perfusion values and delta values over timefor patients that develop pressure ulcers, in accordance with thepresent disclosure.

FIG. 28 depicts example perfusion delta values over time for patientsthat develop pressure ulcers in the heels, in accordance with thepresent disclosure.

FIGS. 29A, 29B, 29C, and 29D illustrate various pressure points on apatient's body at different positions.

DETAILED DESCRIPTION

This description is not intended to be a detailed catalog of all thedifferent ways in which the disclosure may be implemented, or all thefeatures that may be added to the instant disclosure. For example,features illustrated with respect to one embodiment may be incorporatedinto other embodiment, and features illustrated with respect to aparticular embodiment may be deleted from that embodiment. Thus, thedisclosure contemplates that in some embodiments of the disclosure, anyfeature or combination of features set forth herein can be excluded oromitted. In addition, numerous variations and additions to the variousembodiments suggested herein will be apparent to those skilled in theart in light of the instant disclosure, which do not depart from theinstant disclosure. In other instances, well-known structures,interfaces, and processes have not been shown in detail in order not tounnecessarily obscure the invention. It is intended that no part of thisspecification be construed to effect a disavowal of any part of the fullscope of the invention. Hence, the following descriptions are intendedto illustrate some particular embodiments of the disclosure, and not toexhaustively specify all permutations, combinations and variationsthereof.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. The terminology used in thedescription of the disclosure herein is for the purpose of describingparticular aspects or embodiments only and is not intended to belimiting of the disclosure.

All publications, patent applications, patents and other referencescited herein are incorporated by reference in their entireties for theteachings relevant to the sentence and/or paragraph in which thereference is presented. References to techniques employed herein areintended to refer to the techniques as commonly understood in the art,including variations on those techniques or substitutions of equivalenttechniques that would be apparent to one of skill in the art.

Unless the context indicates otherwise, it is specifically intended thatthe various features of the disclosure described herein can be used inany combination. Moreover, the present disclosure also contemplates thatin some embodiments of the disclosure, any feature or combination offeatures set forth herein can be excluded or omitted.

The methods disclosed herein include and comprise one or more steps oractions for achieving the described method. The method steps and/oractions may be interchanged with one another without departing from thescope of the present disclosure. In other words, unless a specific orderof steps or actions is required for proper operation of the embodiment,the order and/or use of specific steps and/or actions may be modifiedwithout departing from the scope of the present disclosure.

As used in the description of the disclosure and the appended claims,the singular forms “a,” “an” and “the” are intended to include theplural forms as well, unless the context clearly indicates otherwise.

As used herein, “and/or” refers to and encompasses any and all possiblecombinations of one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

The terms “about” and “approximately” as used herein when referring to ameasurable value such as a length, a frequency, or a perfusion value andthe like, is meant to encompass variations of ±20%, ±10%, ±5%, ±1%,±0.5%, or even ±0.1% of the specified amount.

As used herein, phrases such as “between X and Y” and “between about Xand Y” should be interpreted to include X and Y. As used herein, phrasessuch as “between about X and Y” mean “between about X and about Y” andphrases such as “from about X to Y” mean “from about X to about Y.”

As used herein, the term “exemplary” is used to mean serving as anexample, instance, or illustration. Any embodiment or aspect describedas “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or aspects, nor is it meant topreclude equivalent structures and techniques known to those of ordinaryskill in the art. Rather, use of the word exemplary is intended topresent concepts in a concrete fashion, and the disclosed subject matteris not limited by such examples.

As used herein, the term “patient” comprises both human and animalsubjects.

As used herein, the term “skin” indicates the surface of a patient'sbody.

As used herein, the term “tissue” includes a plurality of layers of thepatient's body starting from the stratum corneum and includingadditional deeper structures such as the epidermis, the dermis, and aportion of deeper tissue that includes blood vessels. In an aspect,tissue does not include the outermost surface of a patient's body.

As used herein, the term “wound” refers to damaged or injured tissue,which may or may not be visible on the surface of the skin. A wound maybe open or closed. A wound may arise from a surgical procedure. A woundmay be a burn wound. In an aspect, a wound is a pressure ulcer. In afurther aspect, the pressure ulcer is subcutaneous. In one aspect, apressure ulcer is a pressure ulcer resulting from an extended period ofuse of a medical device such as, for example, a mask, a tubing, or astrap. In an aspect, a wound is a diabetic foot ulcer. In an aspect, awound is a vascular ulcer.

As used herein, the term “delta” refers to a calculated differencebetween two values derived from measurements obtained approximately thesame time from a subject. In an aspect, each of the values is asummation value calculated from measurements obtained approximately thesame time. In an aspect, measurements are obtained approximately thesame time when they are taken within about one hour, such as less thanabout 30 minutes, less than about 20 minutes, less than about 10minutes, less than about 5 minutes, less than about 4 minutes, less thanabout 3 minutes, less than about 2 minutes, less than about 1 minute, orless than about 30 seconds.

As used herein, the term “time delta” refers to a calculated differencebetween two values derived from measurements obtained at different timefrom a subject. In an aspect, each of the values is an average valuecalculated from measurements obtained approximately the same time. In anaspect, each of the values is a summation value calculated frommeasurements obtained approximately the same time. In an aspect,measurements are obtained approximately the same time when they aretaken apart by more than about one hour, such as more than about 2hours, such as more than about 3 hours, such as more than about 4 hours,such as more than about 5 hours, such as more than about 6 hours, suchas more than about 8 hours, or such as more than about 10 hours.

As used herein, the variables “K,” “L,” “M,” and “N” are non-negativeintegers.

As used herein, the term “anatomy-specific” refers to the application ofclinical interventions to the same locations where certain perfusion orSpO₂ measurements are taken.

As used herein, a “system” may be a collection of devices in wired orwireless communication with each other.

As used herein, “bisymmetric” refers to a pair of locations that areapproximately equidistant from a line of symmetry.

As used herein, the term “camera” comprises any device that capturesindependent information about a plurality of points distributed across atwo-dimensional area without contacting the points.

As used herein, the term “light” means electromagnetic energy having awavelength within the range of 1 picometer to 1 meter. In an aspect,this range is 1 nanometer to 1 millimeter, encompassing “ultraviolet,”“visible,” and “infrared” light. In an aspect, this range is 10-390nanometers, which is commonly understood to be “ultraviolet” light. Inan aspect, this range is 390-700 nanometers, which is commonlyunderstood to be “visible” light. In an aspect, this range is 700nanometers to 1 millimeter, which is commonly understood to be“infrared” radiation. In an aspect, this range is 700-900 nanometers,which is commonly understood to be “near infrared” radiation. In anaspect, this light may be a narrow band of wavelengths about aparticular wavelength. In an aspect, the particular wavelength is 760and/or 830 nanometers.

Within this document, identification of light as having a certainwavelength has the same meaning as identifying the light as having acertain frequency, as the wavelength and frequency of light are uniquelyrelated. Reference to a frequency of light is considered equivalent andinterchangeable with a reference to the wavelength of the same light.

As used herein, the term “method” comprises a sequence of activities,e.g. steps. In certain embodiments, the steps must be performed in aparticular order while, in other embodiments, the sequence of activitiesmay be interchanged. A “method” is considered equivalent to andinterchangeable with a “process.” In certain embodiments, one or moredisclosed steps are omitted.

Perfusion and Oxygenation Measurements

FIG. 1 depicts the tissue around a burn 102 in tissue 100 of a patient.Tissue 100 has a surface epidermis layer 110, a layer of dermis 120, anda subcutaneous layer 130. Blood vessels 180 in layer 130 connect toarterioles 182 that penetrate layers 120 and 110.

Burn 102 has a central region 150 that is a “zone of necrosis,” which isprimarily dead tissue with a low moisture content. Surrounding region150 is a region 160 that is a “zone of stasis,” which is tissue that ischaracterized by decreased tissue perfusion. The tissue in region 160 ispotentially salvageable and is of particular interest to a clinician asthis is the area of focus in treating a burn. The next region 170 is azone of hyperemia wherein tissue perfusion is increased because localproduction of inflammatory mediators in region 170 causes dilatation ofblood vessels.

FIGS. 2A and 2B depict a skin flap 240 created as part of breastreconstruction surgery. In this example, a section of skin 210 isremoved from the back over the latissimus dorsi muscle 220 as shown inFIG. 2A. Skin 210 is placed in location 240 to provide additionalsurface to cover the implant 230 as shown in FIG. 2B. Location 222 inFIG. 2B indicates the location from which flap 210 was removed.

FIG. 3 is a representative plot 300 of the absorption spectrum ofoxygenated hemoglobin 310 and de-oxygenated hemoglobin 312. Oxygenatedcurve 310 has a local peak 320 at 760 nanometers, which creates adifference between the local maximum of curve 310 and curve 312 at thiswavelength. At 830 nanometers, curve 310 has a local minimum 322 thatalso creates a local maximum in the difference between curves 310 and312. Lasers are commonly available that emit light having a wavelengthin the range of 760-830 nanometers.

FIG. 4 depicts a block diagram of an example perfusion measurementdevice 400, in accordance with the present disclosure. Device 400comprises a processor 440 that is connected to a display 410 and userinterface 480. Processor 440 is also coupled to a memory 450, acommunication module 460, an emitter 420, and a receiver 430.

In an aspect, memory 450 is nonvolatile and contains instructions that,when loaded into and executed on processor 440, cause processor 440 toexecute one or more steps of a process.

In an aspect, emitter 420 is configured to emit light and receiver 430is configured to detect light. In an aspect, receiver 430 provides asignal to the processor 440 that comprising information about thereceived light. In one aspect, this information comprises one or moredata selected from the group consisting of a value of the intensity ofthe detected light, a wavelength of the detected light, a timing of thedetected light, and a duration of the detected light.

In an aspect, emitter 420 and/or receiver 430 comprise a filter (notvisible in FIG. 4 ) that passes only light having a wavelength withinone or more defined ranges. In an aspect, there are multiple emitters420 and/or multiple receivers 430 that emit and detect light at a commonwavelength or at different frequencies. For example, a first emitter 420emits light at 760 nanometers while a second emitter 420 emits light at830 nanometers. In an aspect, a single emitter 420 emits light at both760 and 830 nanometers. For example, a first receiver 430 detects lightat 760 nanometers while a second receiver 430 detects light at 830nanometers. In an aspect, a single receiver detects light at both 760and 830 nanometers.

FIG. 5 depicts an exemplary configuration of a perfusion measurementdevice 500, in accordance with the present disclosure. Device 500comprises a substrate 502 to which are attached an emitter 501 and aplurality of receivers 510, 512, 514, 516, 518, and 520. Receiver 510 isspaced apart from emitter 501 by a first distance D1 while receivers 510and 512 are spaced apart by a second distance D2. In an aspect,substrate 502 is flexible as shown in FIG. 5 . In another aspect,substrate 502 is rigid and/or comprises a rigid element.

FIG. 6 depicts a schematic cross-section of tissue 601 showing how lightemitted by emitter 610 is reflected by the tissue 601, in accordancewith the present disclosure. The light 612A is emitted at a firstintensity. Part of light 612A is reflected at a first depth as light614A while the remainder continues as light 612B. Similarly, part oflight 612B is reflected a second depth as light 614B while the remaindercontinues as light 612C. In this example, a portion of light 612C isreflected as light 614C while the remainder is lost in the deeper tissue601.

Still referring to FIG. 6 , receivers 620, 622, and 624 are placed atdistances from emitter 610 such that they respectively receive light614A, 614B, and 614C. The intensity of each light 614A, 614B, and 614Ccomprises information about the tissue along the entire respective pathfrom the emitter 610 to the particular receiver. In an aspect,information about the portion of the path of light 612B that is belowlight 612A and above light 612C is extracted by comparing theinformation about the light detected by receiver 622 to one or both ofthe light 614A and 614C that are received by receivers 620 and 624. Inan aspect, this comparison is made by subtraction of the intensity ofthe light received by receiver 620 from the intensity of the lightreceived by receiver 622. In an aspect, the information to be comparedcomprises intensities of one or more of light 614A, 614B, and 614C.

FIG. 7 depicts the emitted signal 710 and detected signals 720, 730, and740 of an example system 700, in accordance with the present disclosure.In this example, signal 720 is detected by a first receiver and has peakvalue 724, signal 730 is detected by a second receiver and has peakvalue 734, and signal 740 is detected by a third receiver and has peakvalue 744. As shown in FIG. 7 , peak values 724, 734, and 744 aretime-shifted from the emitted pulse in relation to the path length ofthe light from the emitter to the respective receiver. In this example,waveforms of signals 720, 730, and 740 have shapes that reflectdetection of light that has traveled on multiple different paths fromthe emitter to the respective receiver.

In an aspect, time windows 722, 732, and 742 are imposed on the signals720, 730, and 740 to detect only light that has traveled along a definedpath from the emitter to the receiver. In one aspect, multiple timewindows (not shown in FIG. 7 ) are imposed on a single signal to captureinformation about light that has traveled on different paths.

FIG. 8 depicts example paths 812A, 812B, and 812C of reflected lightwith a wide-angle source in emitter 810, in accordance with the presentdisclosure. A wide-angle source emits light over a solid angle, forexample a 30 degree cone. In an aspect, this cone may be orientedvertically, i.e. perpendicular to the skin, while in another aspect thecone may be at an angle to the skin. In one aspect, the emitted lightmay be non-symmetric about an axis.

Beams of light 812A, 812B, and 812C are each emitted at differentangles. At an example depth 830, for example at the bottom of the dermislayer 120, light beams 814A,814B, and 814C are reflected in a diffusemanner from the respective beams 812A, 912B, and 812C toward a commonreceiver 820. Similarly at depth 840, for example at the bottom ofsubcutaneous layer 130, beams 816A, 816B, and 816C are reflected towardthe same receiver 820. The light detected by receiver 820 contains timeand intensity information about light that has followed multiple pathsfrom the emitter 810.

FIG. 9 depicts emitted signal 910 and detected signals 914A and 916C ofa system similar to that of FIG. 8 , in accordance with the presentdisclosure. In this example, the emitter emits a pulse of light 940 thatcomprises light at two frequencies. Light at the first wavelength 914Ais detected as pulse 944A and light at the second wavelength is detectedas pulse 946C. In an aspect, the timing of pulses 944A and 946A areadjusted before being summed together. In another aspect, the timing ofpulses 944A and 946A are not adjusted before being summed together.

In an aspect, signals 914A and 916C are added together to form signal920 that represents the timing and intensity of light reflected fromboth oxygenated and de-oxygenated hemoglobin.

FIGS. 10A and 10B depict the detected signals of light reflected atvarious points located across a wound from oxygenated hemoglobin 1020and de-oxygenated hemoglobin 1010, in accordance with the presentdisclosure. FIG. 10A is a representation of a true continuous signalwhile FIG. 10B is a representation of calculations made withmeasurements made at discrete points along the same line.

In FIG. 10B, at location 1030, the white dot 1050 is the ratio of theintensities of the oxygenated to the de-oxygenated wavelengths and isplotted with reference to the left scale “oxygenation.” In an aspect, aratio of the intensities of the oxygenated to the de-oxygenatedwavelengths can be converted into an SpO₂ value, indicating thepercentage of oxygenated blood at a local site. At the same location1030, the black dot 1060 is the summation of the intensities of the twowavelengths and is plotted with reference to the right scale“perfusion.” The information provided by the summation 1060, whichsuggests fair-to-poor perfusion at location 1030, gives a differentperspective than the ratio 1050, which suggests a high level ofoxygenation. In practice using existing ratio methodology, a high levelof oxygenation is often regarded as a sign of good perfusion, and viceversa. However, in this example, data obtained using the method of thepresent disclosure shows that the area of high level of oxygenation isactually poorly perfused, and the area of low level of oxygenation isactually very well perfused.

Still referring to FIG. 10B, at location 1040, the oxygenation ratio1052 suggests that oxygenation levels are lower than optimal, while theperfusion summation 1062, which is the summation of the intensities ofthe two wavelengths, suggest that perfusion is good. Again, theprovision of information on the total amount of both oxygenated andde-oxygenated hemoglobin gives a different perspective than the simpleratio of one to the other.

FIGS. 11A and 11B depict the detected signals of light reflected fromoxygenated hemoglobin 1101 and de-oxygenated hemoglobin 1102 along aline across a wound, in accordance with the present disclosure. Points1120, 1122, 1124, 1126, and 1128 are five locations identified along theline. In an aspect, a line across a wound may be drawn in any direction.In an aspect, any number of locations may be identified along the linefor measurement, for example, up to 100 locations, such as up to 95locations, up to 90 locations, up to 85 locations, up to 80 locations,up to 75 locations, up to 70 locations, up to 65 locations, up to 60locations, up to 55 locations, up to 50 locations, up to 45 locations,up to 40 locations, up to 35 locations, up to 30 locations, up to 25locations, up to 20 locations, up to 15 locations, up to 10 locations,up to 9 locations, up to 8 locations, up to 7 locations, up to 6locations, up to 5 locations, up to 4 locations, up to 3 locations, upto 2 locations, or 1 location. In an aspect, locations identified alonga line may be spaced approximately equidistance apart. In an aspect,locations identified along a line may be spaced unevenly apart. In anaspect, a subgroup of locations identified along a line may be spacedapproximately equidistance apart. In an aspect, a subgroup of locationsidentified along a line may be unevenly spaced apart. In an aspect,multiple lines across a wound may be drawn for measurements. In anaspect, up to 100 lines may be drawn for measurements, such as up to 95lines, up to 90 lines, up to 85 lines, up to 80 lines, up to 75 lines,up to 70 lines, up to 65 lines, up to 60 lines, up to 55 lines, up to 50lines, up to 45 lines, up to 40 lines, up to 35 lines, up to 30 lines,up to 25 lines, up to 20 lines, up to 15 lines, up to 10 lines, up to 9lines, up to 8 lines, up to 7 lines, up to 6 lines, up to 5 lines, up to4 lines, up to 3 lines, up to 2 lines, or 1 line. In an aspect, linesdrawn across the wound may have approximately the same angles betweenthem. In an aspect, lines drawn across the wound may have differentangles between them. In an aspect, a subgroup of lines drawn across thewound may have approximately the same angles between them. In an aspect,a subgroup of lines drawn across the wound may have different anglesbetween them.

FIG. 11C is a plot 1100 of comparative points 1120, 1122, 1124, 1126,and 1128 of the curves 1101 and 1102 of FIGS. 11A and 11B, in accordancewith the present disclosure. The white dots 1130, 1132, 1134, 1136, and1138 connected by reference line 1131 are the oxygenation ratio (ratioof the value in curve 1101 to curve 1102 at the specified locationpoint) and are plotted with reference to the left vertical axis“oxygenation.” The black dots 1140, 1142, 1144, 1146, and 1148 connectedby reference line 1141 are the summation values of curves 1101 and 1102and are plotted with reference to the right vertical axis “perfusion.”

In an aspect, in evaluating the state of a wound by inspection of thelines 1131 and 1141, a clinician could come to different assessments ofthe size and condition of the wound based on the shape of the lines 1131and 1141. In this example, the perfusion information of line 1141suggests a smaller, narrower wound, compared to line 1131. If theclinician were to proceed to attempt to remove the necrotic tissue ofzone 150, with reference to FIG. 1 , the clinician can remove moretissue if guided by line 1131 than if guided by line 1141. This mayresult in the unintended removal of some of the tissue in the zone ofstasis 160, which may increase the healing and final state of the wound.

In this example, the outermost measurement point, shown as 1140 in FIG.11D, is outside the affected area of the wound and none of the othermeasurements are larger than the value of measurement 1140, indicatingthat no measurement was taken in the zone of hyperemia. Referring toFIG. 11C, line 1150 represents the value of the largest summation valueof the measurements at the two frequencies in this example, which inthis example is the summation value 1140. If the line of measurementpoints is extended beyond the visible area of wound damage, theoutermost measurement point is likely to be over healthy unaffectedtissue. The measurement at a point over healthy tissue forms a baselinevalue to which measurements in the affected areas may be compared.Similarly, a summation value of measurements made at two frequencies ata point over healthy tissue forms a baseline summation value. As damagedtissue inherently has perfusion that varies from the normal, eitherincreased perfusion in the zone of hyperemia or reduced perfusion in thezones of stasis or necrosis, comparison of the summation value at apoint in the affected area around a wound to a summation value ofhealthy tissue improves the accuracy of the assessment. Comparison oftwo summation values taken at approximately the same time by the sameperson using the same equipment removes “common mode” factors that wouldaffect all measurements such as whether the patient is active orin-active, dehydrated, or suffering from general blood loss. Comparingthe affected area to a healthy are gives a better picture of the degreeof damage.

A delta value 1152 exists between this largest summation value and thesummation value 1142. Other delta values 1154, 1156, and 1158 existbetween the largest summation value 1150 and the individual summationvalues 1144,1146, and 1148.

FIG. 11E depicts an example plot 1107 of perfusion summation valuestaken across a different wound (not shown), in accordance with thepresent disclosure. Summation value 1172 has been taken over knownhealthy tissue. Summation value 1174 has been taken nearer to the woundand the increase in value, compared to the value of 1174, is anindication that this location is in the zone of hyperemia. The near-zerovalue of summation value 1176 indicates that this is likely in the zoneof necrosis. The values of 1178 and 1180, being lower than 1172 whilehigher than 1176, indicate that these may in the zone of stasis. Theshape of the curve 1182 provides guidance to a clinician as to thenature of the underlying tissue at and between the points ofmeasurement.

If a measurement location is within the zone of hyperemia, the summationvalue may be higher than the summation value of healthy tissue. In thiscase, the “baseline” value of line 1150 in FIG. 11C may be selected asthe outermost point, such as location 1140 in FIG. 11D, or from a pointspecifically selected as a location over healthy unaffected tissue. Inan aspect, the baseline value to which other summation values arecompared is the value associated with known healthy tissue, which maynot the largest summation value.

In an aspect, a user may take repeated measurements to map the zone ofhyperemia as indicated by the summation value, e.g. the perfusion, beinghigher than a baseline value taken over known healthy tissue. Thelocations may be captured via a manual method, e.g. marking on a drawingor picture of the wound, or via a location sensing system, e.g. using a3D accelerometer-based location determination system. Alternately, theperfusion measurement device may incorporate a marking capability suchthat a user may trigger a mark to be applied to the skin. The user maydo this manually. In an aspect, the perfusion measurement device mayautomatically apply the mark when the summation value exceeds athreshold. The threshold may be set while taking a perfusion measurementover known healthy tissue. In an aspect, the threshold may be entereddirectly by the user.

In the example of FIG. 11E, the baseline value would be chosen to be thevalue 1172 and delta values would be calculated for summation values1174, 1176, 1178, and 1180. In an aspect, the delta values would bereported as positive values for point 1174 and negative values forpoints 1176, 1178, and 1180. In an aspect, the polarity of the deltavalues would be reversed. In one aspect, only absolute values of thedelta are reported.

In an aspect, multiple measurements are taken at a chosen location ateach selected wavelength. In an aspect, multiple measurements taken at achosen location at each selected wavelength are averaged together beforesummation according to the present disclosure. In an aspect, each set ofmeasurements consisting of measurements taken at a chosen location atall the selected wavelengths are first summed together, and then anaverage summation value is determined by averaging the sum obtained fromeach set of measurements.

In an aspect, a delta value is determined by subtraction of a summationvalue from a baseline value. In an aspect, a baseline value is selectedin accordance with the method of the description provided herein. In anaspect, a baseline value is calculated by an average of summation valuesobtained at locations outside a wound. In an expect, a baseline value iscalculated by an average of all the summation values obtained bothinside and outside a wound. In an aspect, a delta value is determined bysubtraction of an average summation value at a site from a baselinevalue. In an aspect, a delta value is determined by subtraction of theminimum summation value at a site from the baseline value. In an aspect,a delta value is determined by subtraction of the minimum summationvalue at a site from the maximum summation value. In an aspect, apercentage value for each summation value relative to a largestsummation value in the series of summation values is further determined.

FIG. 11D depict an example wound 1105 and an exemplary map of the lineof measurements of the plot of FIG. 11C, in accordance with the presentdisclosure system. The dots 1140, 1142, 1144, 1146, and 148 correspondto the locations 1120, 1122, 1124, 1126, and 1128 of FIGS. 11A and 11B.The zone of necrosis 1164 and the zone of hyperemia 1160 reflect theinformation provided by line 1141. The zone 1162 schematicallyillustrates a comparative zone of necrosis associated with theoxygenation line 1131, which is larger and wider than theperfusion-guided zone 1164.

FIGS. 12A, 12B, 12C, and 12D depict examples of the disclosed apparatus,in accordance with the present disclosure.

FIG. 12A is an example handheld device 1200 having a single emitter 1202and two receivers 1204 disposed, in this example on opposite sides ofthe emitter 1202. The emitter 1202 and receivers 1204 are mounted on arigid substrate.

FIG. 12B depicts an example bandage 1210 wherein emitters 1202 andreceivers 1204 are disposed on a flexible absorbent pad 1206 with anadhesive backing 1208 intended to retain the bandage on the skin of apatient in a fixed location. Repeated measurements of the reflectedlight by the receivers 1204 over time enables tracking of the conditionof the wound.

FIG. 12C depicts a substrate 1210 with an array of emitters 1202 andreceivers 1204 arranged in a grid. In an aspect, a single emitter 1202is activated while one or more of the surrounding receivers 1204 sensethe reflected light. In an aspect, different emitters 1202 emitdifferent wavelengths of light.

FIG. 12D depicts a system 1230 that comprises one or more emitters 1236emitting beams 1238 of light with one or more receivers 1232 each havinga field-of-view 1234. In an aspect, the receivers 1232 are image-formingcameras that optically detect the intensity of the light reaching thesurface of the skin around wound 1250. In an aspect, the emitters 1236emit different wavelengths of light. In an aspect, the emitters 1236 areactivated at different and non-overlapping times and the receivers 1232can detect the reflected light of either wavelength.

FIG. 13 is a flowchart 1300 of an exemplary method of perfusionmeasurement, in accordance with the present disclosure. The processprogresses from the START step 1302 to step 1304 of measuring the amountof oxygenated and de-oxygenated hemoglobin at one or more depths belowthe skin. In an aspect, these measurements are derived from comparisonof signals from a plurality of receivers arranged around a singleemitter. In step 1306, which may precede or performed in parallel withstep 1304, the location is determined. Step 1308 sums the measurementsassociated with oxygenated and de-oxygenated hemoglobin. Step 1310optionally adjusts the summation value by comparison with informationregarding light that reached the receivers via alternate paths throughthe tissue. The raw and adjusted values are recorded in step 1312. Ifmore readings are to be taken around the site of injury, the processbranches at step 1314 to the “NO” path 1316 and returns to step 1304. Ifall measurements are complete, the process branches at step 1314 to the“YES” path 1318 to step 1320 where a delta value is calculated as thedifference between the highest perfusion value, which will be associatedwith healthy tissue, and the various other measurements around thecommon site. These delta values are plotted in step 1322 and represent adegration of perfusion as compared to the a baseline of healthy tissuefor this patient at this time at this location with this instrument asoperated by this user. The process terminates in step 1324 “FINISH.”

Selection of a Strategy for Tissue Damage Intervention Using Perfusionor Oxygenation Measurements

FIG. 14 depicts an overall process 1400 for selecting a wound treatmentstrategy based on measured perfusion or oxygenation values of blood intissue below a patient's skin in accordance with this disclosure, fromadmission to a care facility until discharge from the care facility. Inan aspect, a wound is a pressure ulcer. In one aspect, a pressure ulceris a pressure ulcer resulting from an extended period of use of amedical device such as, for example, a mask, a tubing, or a strap. In anaspect, a wound is a diabetic foot ulcer. In an aspect, a wound is avascular ulcer. In an aspect, a wound is a burn wound. In an aspect, acare facility is selected from the group consisting of a hospital, arecovery facility, an assisted living facility, a residential carefacility, a nursing home, a long-term care facility, a continuing carecommunity, and an independent living community. In an aspect, a carefacility may be a home or other residence of the patient, whereupon the“admit” step 1402 will be a first evaluation of a patient at their homeby a nurse or other caregiver. In one aspect, the schedule ofinterventions and evaluation intervals used in a home setting may bedifferent than the corresponding interventions and intervals used at ahospital.

In an aspect, in process 1400, a newly admitted patient receives anintake evaluation in step 1404 that includes one or more of a visualexamination of a portion of the patient's skin, completion of at least aportion of a risk assessment protocol that evaluates one or more ofnutrition, mobility, physical activity, physical strength, and abilityto communicate, and blood perfusion measurements made in one or morelocations on the patient's skin. In an aspect, the perfusionmeasurements may include making a plurality of perfusion measurements ata single “location” on the patient's skin. In an aspect, an SpO₂ valueis determined from converting a ratio of the intensities of theoxygenated to the de-oxygenated wavelengths measured in the process ofthe prefusion measurements. In an aspect, an SpO₂ value In one aspect,“location” is considered as an area rather than a single point such thatperfusion measurements may be made at spatially separated points withinthe location. For example, a “heel” location includes the medial,lateral, and posterior surfaces around the heel as well as the posteriorportion of the sole of that foot.

In one aspect, once the evaluation step is complete, a determination ismade in step 106 as to whether the patient's readings are abnormal,i.e., whether the combination of the results of the various elements ofthe evaluation indicate that the patient has, or is at risk ofdeveloping, further wound tissue damage. Each element of the evaluationmay have an individual criterion for level of risk, for example ascoring system with threshold value that indicates an unacceptable risk.In an aspect, there is a protocol to combine the criteria to generate acomposite parameter that can be used to select a level of intervention.

In an aspect, if the patient is determined to be at an acceptable levelof risk, the process branches to step 1408 which implements the lowestlevel of intervention, designated herein as “level-zero” or “level-0.”Progressing through steps 1410 and 1412, the patient will be reassessedusing at least the perfusion or oxygenation measurement protocol in step1414 at a frequency, or conversely a time interval, associated withlevel-0. The process 1400 then loops back to step 1406 to evaluate theresults of the perfusion or oxygenation measurements made in step 1414.

In one aspect, if the patient is determined in step 1406 to haveabnormal readings, then the process branches to step 1422, whichimplements a higher level of intervention. In an aspect, there is adefined hierarchy of intervention levels, with each level implementing amore intensive intervention than the next-lower level. In an aspect,each level also has a defined monitoring interval or frequencyindicating how often a set of perfusion or oxygenation measurementsshould be made, where higher levels will generally have shorterintervals. In this example, the process has been defined by thehospital, or other administering organization, to step up one level to alevel-1 intervention at this point. In another aspect, step 1422 mayimplement a level-2 or higher level of intervention. The process nowenters a new loop starting at step 1430 where the patient will now bemonitored at a level-N frequency where N is in the range of 1 to n, nbeing the highest defined level of intervention and monitoring.

In an aspect, at step 1434, the patient's history is evaluated todetermine whether their condition is improving. If the patient'scondition is improving, for example as evidenced by a decreasing deltavalue for perfusion measurements, then the process branches to step1442. In this example, step 1442 continues to implement the currentlevel of intervention and the process loops through step 1440 to steps1430-1432-1434-1442-1440 until the delta value drops below thethreshold. In an aspect, the level of intervention may be reduced instep 1442 based on the magnitude of the delta value as the delta valuetrends downward. In an aspect, the patient's condition is improving ifoxygenation measurements are consistently at or above 95% oxygenated.

In one aspect, if the patient does not show improvement in step 1434,the process branches to an increase in the level of intervention in step1438 provided that the skin is not broken, i.e., an open wound has notdeveloped, in step 1436. If an open wound has developed, perfusionmeasurements will now be made around the periphery of the open wound instep 1444 to map inflammation or other precursor indication of the woundenlarging. The open wound itself is treated in step 1448 and thissecondary loop 1444-1446-1448-1450 continues until the wound closes,whereupon the process returns to step 1430.

In an aspect, at any time in process 100, discharge of the patientbranches to step 1418, where the condition of the patient upon dischargeor transfer is documented. In an aspect, step 1418 comprises a final setof perfusion measurements at one or more locations on the patient'sbody. In one aspect, a final set of oxygenation measurements at one ormore locations on the patient's body is made. In an aspect, theselocations include areas that were not receiving an intervention and werenot previously identified as at risk. In an aspect, this information isprovided to the receiving caregiver. The patient is then discharged ortransferred in step 120.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of woundintervention, the method comprising the steps of: evaluating a patientfor a risk of tissue damage upon admission to a care facility, where theevaluating step comprises making a first plurality of perfusionmeasurements in the patient, calculating a first delta value from aportion of the first plurality of perfusion measurements, determiningwhether the first delta value exceeds a first threshold, administering afirst intervention of level-0 if the first delta value does not exceedthe first threshold, and administering a first intervention of level-Nif the first delta value exceeds the first threshold, where N is aninteger and N has a value of 1 or greater.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of woundintervention, the method comprising the steps of: evaluating a patientfor a risk of tissue damage upon admission to a care facility, where theevaluating step comprises making a first plurality of SpO₂ measurementsin the patient, determining whether any of the first plurality of SpO₂measurements is below a first threshold, administering a firstintervention of level-0 if the first plurality of SpO₂ measurements areat or above the first threshold, and administering a first interventionof level-N if any of the first plurality of SpO₂ measurements is belowthe first threshold, where N is an integer and N has a value of 1 orgreater. In an aspect, a first threshold for SpO₂ measurements is about95%. In one aspect, a first threshold SpO₂ measurements is about 95.5%,about 96%, about 96.5%, about 97%, about 97.5%, or about 98%.

In one aspect, a first plurality of perfusion measurements is taken atand around one or more anatomical sites selected from the groupconsisting of a sternum, a sacrum, a heel, a scapula, an elbow, an ear,and other fleshy tissues of a patient. In an aspect, a first pluralityof perfusion measurements is taken at and around one or more anatomicalsites at risk of tissue injury. In an aspect, a first plurality ofperfusion measurements is taken at and around all anatomical sites atrisk of tissue injury. FIGS. 29A, 29B, 29C, and 29D illustrate locationsof tissue injury risk in circles for patients in different positions. Inan aspect, a first plurality of perfusion measurements is taken at andaround one or more anatomical sites in long-term contact with a medicaldevice, an anatomical site is selected from the group consisting of acheek, a nose, a chest, a stomach, and a lower abdomen area. In anaspect, a first plurality of perfusion measurements is separated intosub-groups for analysis based on the general location at which ameasurement is taken. In one aspect, a first plurality of perfusionmeasurements is taken at locations located on one or more concentriccircles centered around an anatomical site. In an aspect, a firstplurality of perfusion measurements is taken at locations located on astraight line at approximately equidistance from an anatomical site.

In one aspect, a first delta value is determined by the differencebetween the maximum perfusion value and the minimum perfusion value fromthe first plurality of perfusion measurements collected. In an aspect, afirst delta value is determined by the difference between the maximumperfusion average of measurements taken at one location and the minimumperfusion average of measurements taken at a second location. In oneaspect, a first delta value is determined for a portion of a firstplurality of perfusion measurements made up of a sub-group as defined bylocation taken. In an aspect, an average perfusion value at a locationis obtained from two, three, four, five, six, seven, eight, nine, ten,or more than ten perfusion values measured at that location. In oneaspect, a first delta value is determined by the difference betweenperfusion values derived from measurements taken at two bisymmetriclocations with respect to a centerline.

In an aspect, a delta value may be calculated from a plurality ofperfusion measurements made at a certain location, or in close proximityaround a specific location, in a plurality of methods. In an aspect, aplurality of perfusion measurements are made in a pre-determined patternon the skin and the delta value is calculated by subtracting theperfusion value associated with a pre-determined position within thepattern from the largest perfusion value made at the other positions inthe pattern. In an aspect, a plurality of perfusion measurements aremade in a pre-determined pattern on the skin and the delta value iscalculated by identifying the perfusion value associated with apre-determined position within the pattern and subtracting the largestperfusion value made at the other positions in the pattern. In anaspect, an average perfusion value may be calculated from a portion of aset of perfusion values generated by a plurality of perfusionmeasurements at a single location and a delta value calculated as thelargest difference between the average and a single perfusion value ofthe same set. In an aspect, a delta value may be calculated as a ratioof the largest perfusion value to the smallest perfusion value within aset of perfusion values.

In an aspect, a first threshold may be about 0.3, 0.35, 0.4, 0.45, 0.5,0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1,4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5,5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9,7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In one aspect, a first threshold mayrange from 0.1 to 8.0, such as from 0.1 to 1.0, from 1.1 to 2.0, from2.1 to 3.0, from 3.1 to 4.0, from 4.1 to 5.0, from 5.1 to 6.0, from 6.1to 7.0, from 7.1 to 8.0, from 0.1 to 7.5, from 0.5 to 8.0, from 1.0 to7.0, from 1.5 to 6.5, from 2.0 to 6.0, from 3.0 to 5.5, from 3.5 to 5.0,or from 4.0 to 4.5. In an aspect, a first threshold can be scaled by afactor or a multiple based on the values provided herein. It will beunderstood that a threshold is not limited by design, but rather, one ofordinary skill in the art would be capable of choosing a predeterminedvalue based on a given unit of perfusion. In one aspect, thresholds ofthe present disclosure are varied according to the specific portion of apatient's body on which measurements are being made, or one or morecharacteristics of the patient such as age, height, weight, familyhistory, ethnic group, and other physical characteristics or medicalconditions.

In an aspect, N ranges from 1 to 50, such as from 1 to 2, from 1 to 3,from 1 to 4, from 1 to 5, from 1 to 6, from 1 to 7, from 1 to 8, from 1to 9, from 1 to 10, from 1 to 15, from 1 to 20, from 1 to 25, from 1 to30, from 1 to 35, from 1 to 40, or from 1 to 45.

In one aspect, N is determined by the amount by which the first deltavalue exceeds the first threshold. In an aspect, the amount by which adelta value exceeds a threshold established for (N+1) is greater thanthe amount by which a delta value exceeds a threshold established for N.In one aspect, the amount by which a delta value exceeds a thresholdestablished for (N−1) is less than the amount by which a delta valueexceeds a threshold established for N.

In an aspect, a level-1 (N=1) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 100% ofthe threshold value, such as not more than 95%, not more than 90%, notmore than 85%, not more than 80%, not more than 75%, not more than 70%,not more than 65%, not more than 60%, not more than 55%, not more than50%, not more than 45%, not more than 40%, not more than 35%, not morethan 30%, not more than 25%, not more than 20%, not more than 15%, notmore than 10%, or not more than 5% of the threshold value. In an aspect,a level-1 intervention is applied to a location at which a measurementwas made.

In an aspect, a level-2 (N=2) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 150% ofthe threshold value, such as not more than 145%, not more than 140%, notmore than 135%, not more than 130%, not more than 125%, not more than120%, not more than 115%, not more than 110%, not more than 100%, notmore than 95%, not more than 90%, not more than 85%, not more than 80%,not more than 75%, not more than 70%, not more than 65%, not more than60%, not more than 55%, not more than 50%, not more than 45%, not morethan 40%, not more than 35%, not more than 30%, not more than 25%, notmore than 20%, not more than 15%, not more than 10%, or not more than 5%of the threshold value. In an aspect, a level-2 intervention is appliedto a location at which a measurement was made.

In one aspect, a level-3 (N=3) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 200% ofthe threshold value, such as not more than 195%, not more than 190%, notmore than 185%, not more than 180%, not more than 175%, not more than170%, not more than 165%, not more than 160%, not more than 155%, notmore than 150%, not more than 145%, not more than 140%, not more than135%, not more than 130%, not more than 125%, not more than 120%, notmore than 115%, not more than 110%, not more than 100%, not more than95%, not more than 90%, not more than 85%, not more than 80%, not morethan 75%, not more than 70%, not more than 65%, not more than 60%, notmore than 55%, not more than 50%, not more than 45%, not more than 40%,not more than 35%, not more than 30%, not more than 25%, not more than20%, not more than 15%, not more than 10%, or not more than 5% of thethreshold value. In an aspect, a level-3 intervention is applied to alocation at which a measurement was made.

In one aspect, a level-4 (N=4) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 250% ofthe threshold value, such as not more than 245%, not more than 240%, notmore than 235%, not more than 230%, not more than 225%, not more than220%, not more than 215%, not more than 210%, not more than 205%, notmore than 200%, not more than 195%, not more than 190%, not more than185%, not more than 180%, not more than 175%, not more than 170%, notmore than 165%, not more than 160%, not more than 155%, not more than150%, not more than 145%, not more than 140%, not more than 135%, notmore than 130%, not more than 125%, not more than 120%, not more than115%, not more than 110%, not more than 100%, not more than 95%, notmore than 90%, not more than 85%, not more than 80%, not more than 75%,not more than 70%, not more than 65%, not more than 60%, not more than55%, not more than 50%, not more than 45%, not more than 40%, not morethan 35%, not more than 30%, not more than 25%, not more than 20%, notmore than 15%, not more than 10%, or not more than 5% of the thresholdvalue. In an aspect, a level-4 intervention is applied to a location atwhich a measurement was made.

In one aspect, a level-5 (N=5) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 300% ofthe threshold value, such as not more than 295%, not more than 290%, notmore than 285%, not more than 280%, not more than 275%, not more than270%, not more than 265%, not more than 260%, not more than 255%, notmore than 250%, not more than 245%, not more than 240%, not more than235%, not more than 230%, not more than 225%, not more than 220%, notmore than 215%, not more than 210%, not more than 205%, not more than200%, not more than 195%, not more than 190%, not more than 185%, notmore than 180%, not more than 175%, not more than 170%, not more than165%, not more than 160%, not more than 155%, not more than 150%, notmore than 145%, not more than 140%, not more than 135%, not more than130%, not more than 125%, not more than 120%, not more than 115%, notmore than 110%, not more than 100%, not more than 95%, not more than90%, not more than 85%, not more than 80%, not more than 75%, not morethan 70%, not more than 65%, not more than 60%, not more than 55%, notmore than 50%, not more than 45%, not more than 40%, not more than 35%,not more than 30%, not more than 25%, not more than 20%, not more than15%, not more than 10%, or not more than 5% of the threshold value. Inan aspect, a level-5 intervention is applied to a location at which ameasurement was made.

In one aspect, a level-6 (N=6) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 350% ofthe threshold value, such as not more than 345%, not more than 340%, notmore than 335%, not more than 330%, not more than 325%, not more than320%, not more than 315%, not more than 310%, not more than 305%, notmore than 300%, not more than 295%, not more than 290%, not more than285%, not more than 280%, not more than 275%, not more than 270%, notmore than 265%, not more than 260%, not more than 255%, not more than250%, not more than 245%, not more than 240%, not more than 235%, notmore than 230%, not more than 225%, not more than 220%, not more than215%, not more than 210%, not more than 205%, not more than 200%, notmore than 195%, not more than 190%, not more than 185%, not more than180%, not more than 175%, not more than 170%, not more than 165%, notmore than 160%, not more than 155%, not more than 150%, not more than145%, not more than 140%, not more than 135%, not more than 130%, notmore than 125%, not more than 120%, not more than 115%, not more than110%, not more than 100%, not more than 95%, not more than 90%, not morethan 85%, not more than 80%, not more than 75%, not more than 70%, notmore than 65%, not more than 60%, not more than 55%, not more than 50%,not more than 45%, not more than 40%, not more than 35%, not more than30%, not more than 25%, not more than 20%, not more than 15%, not morethan 10%, or not more than 5% of the threshold value. In an aspect, alevel-6 intervention is applied to a location at which a measurement wasmade.

In one aspect, a level-7 (N=7) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 400% ofthe threshold value, such as not more than 395%, not more than 390%, notmore than 385%, not more than 380%, not more than 375%, not more than370%, not more than 365%, not more than 360%, not more than 355%, notmore than 350%, not more than 345%, not more than 340%, not more than335%, not more than 330%, not more than 325%, not more than 320%, notmore than 315%, not more than 310%, not more than 305%, not more than300%, not more than 295%, not more than 290%, not more than 285%, notmore than 280%, not more than 275%, not more than 270%, not more than265%, not more than 260%, not more than 255%, not more than 250%, notmore than 245%, not more than 240%, not more than 235%, not more than230%, not more than 225%, not more than 220%, not more than 215%, notmore than 210%, not more than 205%, not more than 200%, not more than195%, not more than 190%, not more than 185%, not more than 180%, notmore than 175%, not more than 170%, not more than 165%, not more than160%, not more than 155%, not more than 150%, not more than 145%, notmore than 140%, not more than 135%, not more than 130%, not more than125%, not more than 120%, not more than 115%, not more than 110%, notmore than 100%, not more than 95%, not more than 90%, not more than 85%,not more than 80%, not more than 75%, not more than 70%, not more than65%, not more than 60%, not more than 55%, not more than 50%, not morethan 45%, not more than 40%, not more than 35%, not more than 30%, notmore than 25%, not more than 20%, not more than 15%, not more than 10%,or not more than 5% of the threshold value. In an aspect, a level-7intervention is applied to a location at which a measurement was made.

In one aspect, a level-8 (N=8) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 450% ofthe threshold value, such as not more than 445%, not more than 440%, notmore than 435%, not more than 430%, not more than 425%, not more than420%, not more than 415%, not more than 410%, not more than 405%, notmore than 400%, not more than 395%, not more than 390%, not more than385%, not more than 380%, not more than 375%, not more than 370%, notmore than 365%, not more than 360%, not more than 355%, not more than350%, not more than 345%, not more than 340%, not more than 335%, notmore than 330%, not more than 325%, not more than 320%, not more than315%, not more than 310%, not more than 305%, not more than 300%, notmore than 295%, not more than 290%, not more than 285%, not more than280%, not more than 275%, not more than 270%, not more than 265%, notmore than 260%, not more than 255%, not more than 250%, not more than245%, not more than 240%, not more than 235%, not more than 230%, notmore than 225%, not more than 220%, not more than 215%, not more than210%, not more than 205%, not more than 200%, not more than 195%, notmore than 190%, not more than 185%, not more than 180%, not more than175%, not more than 170%, not more than 165%, not more than 160%, notmore than 155%, not more than 150%, not more than 145%, not more than140%, not more than 135%, not more than 130%, not more than 125%, notmore than 120%, not more than 115%, not more than 110%, not more than100%, not more than 95%, not more than 90%, not more than 85%, not morethan 80%, not more than 75%, not more than 70%, not more than 65%, notmore than 60%, not more than 55%, not more than 50%, not more than 45%,not more than 40%, not more than 35%, not more than 30%, not more than25%, not more than 20%, not more than 15%, not more than 10%, or notmore than 5% of the threshold value. In an aspect, a level-8intervention is applied to a location at which a measurement was made.

In one aspect, a level-9 (N=9) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 500% ofthe threshold value, such as not more than 495%, not more than 490%, notmore than 485%, not more than 480%, not more than 475%, not more than470%, not more than 465%, not more than 460%, not more than 455%, notmore than 450%, not more than 445%, not more than 440%, not more than435%, not more than 430%, not more than 425%, not more than 420%, notmore than 415%, not more than 410%, not more than 405%, not more than400%, not more than 395%, not more than 390%, not more than 385%, notmore than 380%, not more than 375%, not more than 370%, not more than365%, not more than 360%, not more than 355%, not more than 350%, notmore than 345%, not more than 340%, not more than 335%, not more than330%, not more than 325%, not more than 320%, not more than 315%, notmore than 310%, not more than 305%, not more than 300%, not more than295%, not more than 290%, not more than 285%, not more than 280%, notmore than 275%, not more than 270%, not more than 265%, not more than260%, not more than 255%, not more than 250%, not more than 245%, notmore than 240%, not more than 235%, not more than 230%, not more than225%, not more than 220%, not more than 215%, not more than 210%, notmore than 205%, not more than 200%, not more than 195%, not more than190%, not more than 185%, not more than 180%, not more than 175%, notmore than 170%, not more than 165%, not more than 160%, not more than155%, not more than 150%, not more than 145%, not more than 140%, notmore than 135%, not more than 130%, not more than 125%, not more than120%, not more than 115%, not more than 110%, not more than 100%, notmore than 95%, not more than 90%, not more than 85%, not more than 80%,not more than 75%, not more than 70%, not more than 65%, not more than60%, not more than 55%, not more than 50%, not more than 45%, not morethan 40%, not more than 35%, not more than 30%, not more than 25%, notmore than 20%, not more than 15%, not more than 10%, or not more than 5%of the threshold value. In an aspect, a level-9 intervention is appliedto a location at which a measurement was made.

In one aspect, a level-10 (N=10) intervention is applied to a patienthaving a delta value exceeding the threshold by not more than 550% ofthe threshold value, such as not more than 545%, not more than 540%, notmore than 535%, not more than 530%, not more than 525%, not more than520%, not more than 515%, not more than 510%, not more than 505%, notmore than 500%, not more than 495%, not more than 490%, not more than485%, not more than 480%, not more than 475%, not more than 470%, notmore than 465%, not more than 460%, not more than 455%, not more than450%, not more than 445%, not more than 440%, not more than 435%, notmore than 430%, not more than 425%, not more than 420%, not more than415%, not more than 410%, not more than 405%, not more than 400%, notmore than 395%, not more than 390%, not more than 385%, not more than380%, not more than 375%, not more than 370%, not more than 365%, notmore than 360%, not more than 355%, not more than 350%, not more than345%, not more than 340%, not more than 335%, not more than 330%, notmore than 325%, not more than 320%, not more than 315%, not more than310%, not more than 305%, not more than 300%, not more than 295%, notmore than 290%, not more than 285%, not more than 280%, not more than275%, not more than 270%, not more than 265%, not more than 260%, notmore than 255%, not more than 250%, not more than 245%, not more than240%, not more than 235%, not more than 230%, not more than 225%, notmore than 220%, not more than 215%, not more than 210%, not more than205%, not more than 200%, not more than 195%, not more than 190%, notmore than 185%, not more than 180%, not more than 175%, not more than170%, not more than 165%, not more than 160%, not more than 155%, notmore than 150%, not more than 145%, not more than 140%, not more than135%, not more than 130%, not more than 125%, not more than 120%, notmore than 115%, not more than 110%, not more than 100%, not more than95%, not more than 90%, not more than 85%, not more than 80%, not morethan 75%, not more than 70%, not more than 65%, not more than 60%, notmore than 55%, not more than 50%, not more than 45%, not more than 40%,not more than 35%, not more than 30%, not more than 25%, not more than20%, not more than 15%, not more than 10%, or not more than 5% of thethreshold value. In an aspect, a level-10 intervention is applied to alocation at which a measurement was made.

In one aspect, a level-N intervention is more intensive than a level-0intervention. In an aspect, a level-(N+1) intervention is more intensivethan a level-N intervention. In one aspect, a level-(N−1) interventionis less intensive than a level-N intervention.

In an aspect, the evaluating step of the present disclosure furthercomprises performing a visual assessment. In one aspect, the visualassessment is performed in accordance with the guidelines of theNational Pressure Ulcer Advisory Panel (NPUAP).

In one aspect, the evaluating step of the present disclosure furthercomprises performing a risk assessment. In an aspect, the riskassessment is performed in accordance with a test selected from thegroup consisting of the Braden Scale, the Gosnell Scale, the NortonScale, and the Waterlow Scale. In an aspect, the evaluating step of thepresent disclosure further comprises performing an assessment using oneor more objective measurements selected from the group consisting of:sub-epidermal moisture, bioimpedance, ultrasound, pressure measurement;capillary pressure, thermal imaging, spectral imaging, transcutaneouswater loss, and detection of interleukin-1 alpha presence at one or moreanatomic site of interest.

In an aspect, the present disclosure further provides for, and includes,making a second plurality of perfusion measurements in the patient at afirst pre-determined frequency corresponding to the administeredintervention level, calculating a second delta value from a portion ofthe second plurality of perfusion measurements, determining whether thesecond delta value exceeds a second threshold, continuing to administerthe first intervention if the second delta value does not exceed thesecond threshold, continuing to make a plurality of perfusionmeasurements at the first pre-determined frequency if the second deltavalue does not exceed the second threshold, administering a secondintervention of level-M if the second delta value exceeds the secondthreshold, where M is an integer and M is greater than N, and making aplurality of perfusion measurements at a second pre-determined frequencycorresponding to level-M if the second delta value exceeds the secondthreshold.

In an aspect, the present disclosure further provides for, and includes,making a second plurality of SpO₂ measurements in the patient at a firstpre-determined frequency corresponding to the administered interventionlevel, calculating a time delta value based on the differences betweenthe first plurality and the second plurality of SpO₂ measurements,determining whether the time delta value is a decrease exceeding asecond threshold, continuing to administer the first intervention if thetime delta value does not exceed the second threshold, continuing tomake a plurality of perfusion measurements at the first pre-determinedfrequency if the time delta value does not exceed the second threshold,administering a second intervention of level-M if the time delta valueis a decrease exceeding the second threshold, where M is an integer andM is greater than N, and making a plurality of SpO₂ measurements at asecond pre-determined frequency corresponding to level-M if the timedelta value is a decrease exceeding the second threshold.

In one aspect, a pre-determined frequency is selected from the groupconsisting of at least once every 72 hours, at least once every 48hours, at least once every 24 hours, at least once every 12 hours, atleast once every 8 hours, at least once every 6 hours, at least onceevery 4 hours, at least once every 3 hours, at least once every 2 hours,at least once every hour, and at least once every half an hour.

In one aspect, a second plurality of perfusion measurements are taken inaccordance with the description provided herein. In an aspect, a secondplurality of perfusion measurements are made at the same locations wherea first plurality of perfusion measurements were taken. In one aspect, asecond plurality of perfusion measurements are made at some of the samelocations where a first plurality of perfusion measurements were taken.In an aspect, a second plurality of perfusion measurements are made nearthe locations where a first plurality of perfusion measurements weretaken. In one aspect, a second plurality of perfusion measurements aremade at different locations than where a first plurality of perfusionmeasurements were taken.

In an aspect, a second delta value is determined by the differencebetween the maximum perfusion value and the minimum perfusion value fromthe second plurality of perfusion measurements collected. In one aspect,a second delta value is determined by the difference between the maximumaverage of perfusion measurements taken at one location and the minimumaverage of perfusion measurements taken at a second location. In oneaspect, a second delta value is determined for a portion of a secondplurality of perfusion measurements made up of a sub-group as defined bylocation taken.

In an aspect, a second threshold may be about 0.3, 0.35, 0.4, 0.45, 0.5,0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1,4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5,5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9,7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In one aspect, a second threshold mayrange from 0.1 to 8.0, such as from 0.1 to 1.0, from 1.1 to 2.0, from2.1 to 3.0, from 3.1 to 4.0, from 4.1 to 5.0, from 5.1 to 6.0, from 6.1to 7.0, from 7.1 to 8.0, from 0.1 to 7.5, from 0.5 to 8.0, from 1.0 to7.0, from 1.5 to 6.5, from 2.0 to 6.0, from 3.0 to 5.5, from 3.5 to 5.0,or from 4.0 to 4.5. In one aspect, a second threshold for SpO₂measurements may be about 3%, 3.5%, 4%, 5%, 5.5%, 6%, 6.6%, or 7%. In anaspect, a second threshold can be scaled by a factor or a multiple basedon the values provided herein. In one aspect, a second threshold can bethe same as a first threshold. In an aspect, a second threshold can begreater than a first threshold. In one aspect, a second threshold can beless than a first threshold.

In an aspect, M ranges from 2 to 50, such as from 2 to 3, from 2 to 4,from 2 to 5, from 2 to 6, from 2 to 7, from 2 to 8, from 2 to 9, from 2to 10, from 2 to 15, from 2 to 20, from 2 to 25, from 2 to 30, from 2 to35, from 2 to 40, or from 2 to 45.

In one aspect, M is determined by the amount by which the second deltavalue exceeds the second threshold. In an aspect, the amount by which adelta value exceeds a threshold established for (M+1) is greater thanthe amount by which a delta value exceeds a threshold established for M.In one aspect, the amount by which a delta value exceeds a thresholdestablished for (M−1) is less than the amount by which a delta valueexceeds a threshold established for M.

In an aspect, a level M intervention is chosen in accordance with thedescription provided herein, replacing N with M.

In one aspect, the present disclosure further provides for, andincludes, determining whether the second delta value is less than athird threshold, administering a level-(N−1) intervention if the seconddelta value is less than the third threshold and if the firstintervention is not of level-0, and making a plurality of perfusionmeasurements at a pre-determined frequency corresponding to level-(N−1)if the second delta value is less than the third threshold.

In an aspect, the present disclosure further provides for, and includes,determining whether the time delta value is an increase exceeding athird threshold, administering a level-(N−1) intervention if the timedelta value is an increase exceeding the third threshold and if thefirst intervention is not of level-0, and making a plurality of SpO₂measurements at a pre-determined frequency corresponding to level-(N−1)if the time delta value is an increase exceeding the third threshold.

In an aspect, a third threshold may be about 0.3, 0.35, 0.4, 0.45, 0.5,0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1,4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5,5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9,7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In one aspect, a third threshold mayrange from 0.1 to 8.0, such as from 0.1 to 1.0, from 1.1 to 2.0, from2.1 to 3.0, from 3.1 to 4.0, from 4.1 to 5.0, from 5.1 to 6.0, from 6.1to 7.0, from 7.1 to 8.0, from 0.1 to 7.5, from 0.5 to 8.0, from 1.0 to7.0, from 1.5 to 6.5, from 2.0 to 6.0, from 3.0 to 5.5, from 3.5 to 5.0,or from 4.0 to 4.5. In one aspect, a second threshold for SpO₂measurements may be about 3%, 3.5%, 4%, 5%, 5.5%, 6%, 6.6%, or 7%. In anaspect, a third threshold can be scaled by a factor or a multiple basedon the values provided herein. In one aspect, a third threshold can bethe same as a second threshold. In an aspect, a third threshold can begreater than a second threshold. In one aspect, a third threshold can beless than a second threshold. In one aspect, a third threshold can bethe same as a first threshold. In an aspect, a third threshold can begreater than a first threshold. In one aspect, a third threshold can beless than a first threshold.

In an aspect, a second delta value can be 0.1-99.5% of the thirdthreshold, such as 0.1-1%, 0.1-5%, 1-5%, 5-15%, 10-20%, 15-25%, 20-30%,25-35%, 30-40%, 35-45%, 40-50%, 0.1-25%, 15-35%, 25-50%, 25-75%, 45-55%,50-60%, 55-65%, 60-70%, 65-75%, 40-55%, 50-75%, 50-99.5%, 70-80%,75%-85%, 80-90%, 85-95%, 90-99.5%, 65-85%, or 75-99.5% of the thirdthreshold.

In one aspect, the present disclosure provides for, and includes, amethod of slowing the progression of skin and tissue damage in a patientin need thereof, the method comprising the steps of: identifying acurrent intervention of level-K received by the patient, making aplurality of perfusion measurements in the patient, calculating a deltavalue from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a first threshold,continuing to administer the current intervention if the delta valuedoes not exceed the first threshold, continuing to make a plurality ofperfusion measurements at a pre-determined frequency corresponding tolevel-K if the delta value does not exceed the first threshold,administering a new intervention of level-N if the delta value exceedsthe first threshold, where N has a value greater than K, and making aplurality of perfusion measurements at a pre-determined frequencycorresponding to level-N if the delta value exceeds the first threshold.In an aspect, a patient in need thereof is a patient experiencing achange of care, a change in mobility, a change in nutrition, a change insensory perception, or a combination thereof. In one aspect, a patientin need thereof is a patient having developed an open wound. In anaspect, a patient in need thereof is a patient having recovered from anopen wound. In one aspect, a patient in need thereof is a patientreceiving surgery. In an aspect, a patient in need thereof is a patientrecovering from surgery. In an aspect, a patient in need thereof is apatient receiving spinal analgesics or sacral analgesics during asurgery. In one aspect, a patient in need thereof is a patient receivinga surgery for a duration of four or more hours, such as five or morehours, six or more hours, seven or more hours, eight or more hours, nineor more hours, ten or more hours, eleven or more hours, or twelve ormore hours. In an aspect, a surgery has a duration of one or more hours,such as two or more hours, or three or more hours.

In one aspect, a plurality of perfusion measurements are taken inaccordance with the description provided herein. In an aspect, a deltavalue is determined in accordance with the description provided herein.In one aspect, a first threshold is determined in accordance with thedescription provided herein.

In an aspect, K ranges from 2 to 50, such as from 2 to 3, from 2 to 4,from 2 to 5, from 2 to 6, from 2 to 7, from 2 to 8, from 2 to 9, from 2to 10, from 2 to 15, from 2 to 20, from 2 to 25, from 2 to 30, from 2 to35, from 2 to 40, or from 2 to 45.

In an aspect, K is determined by the amount by which the delta valueexceeds the threshold. In an aspect, the amount by which a delta valueexceeds a threshold established for (K+1) is greater than the amount bywhich a delta value exceeds a threshold established for K. In oneaspect, the amount by which a delta value exceeds a thresholdestablished for (K−1) is less than the amount by which a delta valueexceeds a threshold established for K.

In an aspect, a level K intervention is chosen in accordance with thedescription provided herein, replacing N with K.

In an aspect, the present disclosure further provides for, and includes,determining whether the delta value is less than a second threshold,administering a level-L intervention if the delta value is less than thesecond threshold, where L has a non-negative value less than K, andmaking a plurality of perfusion measurements at a pre-determinedfrequency corresponding to level-L if the delta value is less than thesecond threshold.

In an aspect, a second threshold is determined in accordance with thedescription provided herein.

In one aspect, the present disclosure provides for, and includes,determining whether any of the plurality of SpO₂ measurements is abovethe threshold range corresponding to level-K, administering a level-Lintervention if any of the plurality of SpO₂ measurements is above thethreshold range corresponding to level-K, where L has a non-negativevalue less than K, and making a plurality of perfusion measurements at apre-determined frequency corresponding to level-L if any of theplurality of SpO₂ measurements is above the threshold rangecorresponding to level-K. In an aspect, a threshold range is selectedfrom the group consisting of below about 85%, between about 85% to about95%, and above or equal to 95%.

In an aspect, L can be K−1, K−2, K−3, K−4, K−5, K−6, K−7, K−8, K−9, orK−10. In one aspect, L is K−1 if a delta value is 90-99.5% of the secondthreshold, such as 90-95%, 91-96%, 92-97%, 93-98%, 94-99%, or 95-99.5%of the second threshold, unless K−1 is less than 0, in which case Lwould be 0. In an aspect, L is K−2 if a delta value is 80-89.9% of thesecond threshold, such as 80-85%, 81-86%, 82-87%, 83-88%, 84-89%, or85-89.9% of the second threshold, unless K−2 is less than 0, in whichcase L would be 0. In one aspect, L is K−3 if a delta value is 70-79.9%of the second threshold, such as 70-75%, 71-76%, 72-77%, 73-78%, 74-79%,or 75-79.9% of the second threshold, unless K−3 is less than 0, in whichcase L would be 0. In an aspect, L is K−4 if a delta value is 60-69.9%of the second threshold, such as 60-65%, 61-66%, 62-67%, 63-68%, 64-69%,or 65-69.9% of the second threshold, unless K−4 is less than 0, in whichcase L would be 0. In one aspect, L is K−5 if a delta value is 50-59.9%of the second threshold, such as 50-55%, 51-56%, 52-57%, 53-58%, 54-59%,or 55-59.9% of the second threshold, unless K−5 is less than 0, in whichcase L would be 0. In an aspect, L is K−6 if a delta value is 40-49.9%of the second threshold, such as 40-45%,

41-46%, 42-47%, 43-48%, 44-49%, or 45-49.9% of the second threshold,unless K−6 is less than 0, in which case L would be 0. In one aspect, Lis K−7 if a delta value is 30-39.9% of the second threshold, such as30-35%, 31-36%, 32-37%, 33-38%, 34-39%, or 35-39.9% of the secondthreshold, unless K−7 is less than 0, in which case L would be 0. In anaspect, L is K−8 if a delta value is 20-29.9% of the second threshold,such as 20-25%, 21-26%, 22-27%, 23-28%, 24-29%, or 25-29.9% of thesecond threshold, unless K−8 is less than 0, in which case L would be 0.In one aspect, L is K−9 if a delta value is 10-19.9% of the secondthreshold, such as 10-15%, 11-16%, 12-17%, 13-18%, 14-19%, or 15-19.9%of the second threshold, unless K−9 is less than 0, in which case Lwould be 0. In an aspect, L is K−10 if a delta value is 0.1-9.9% of thesecond threshold, such as 0.1-5%, 1-6%, 2-7%, 3-8%, 4-9%, or 5-9.9% ofthe second threshold, unless K−10 is less than 0, in which case L wouldbe 0.

In an aspect, the present disclosure provides for, and includes, amethod of stratifying groups of patients in a care facility based onrisk of tissue damage, the method comprising the steps of: making aplurality of perfusion measurements in each of the patients, calculatinga delta value from a portion of the plurality of perfusion measurementsfor each of the patients, determining whether each delta value exceedsany values in a set of threshold values corresponding to N care levelsand assigning a care level to each of the patients, rearranging thegroup of patients based on each of the patient's assigned care levels.

In an aspect, the present disclosure provides for, and includes, amethod of stratifying groups of patients in a care facility based on therisk of wound development, the method comprising the steps of: making aplurality of SpO₂ measurements in each of the patients, determiningwhether each of the plurality of SpO₂ measurements is below any valuesin a set of threshold values corresponding to N care levels andassigning a care level to each of the patients, and rearranging thegroup of patients based on each of the patient's assigned care levels.

In one aspect, the present disclosure provides for, and includes, amethod of reducing incidence of tissue damage in patients admitted to acare facility, the method comprising the steps of: evaluating a patientfor a risk of tissue damage upon admission to the care facility, wherethe evaluating step comprises making a first plurality of perfusionmeasurements in the patient, calculating a first delta value from aportion of the first plurality of perfusion measurements, determiningwhether the first delta value exceeds a first threshold, administering afirst intervention of level-0 if the first delta value does not exceedthe first threshold, and administering a first intervention of level-Nif the first delta value exceeds the first threshold, where N is aninteger and N has a value of 1 or greater. In an aspect, the presentdisclosure provides for, and includes, a method of reducing theincidence of wound development in patients admitted to a care facility,the method comprising the steps of: evaluating a patient for a risk oftissue damage upon admission to the care facility, where the evaluatingstep comprises making a first plurality of SpO₂ measurements in thepatient, determining whether any of the first plurality of SpO₂measurements is below a first threshold, administering a firstintervention of level-0 if the first plurality of SpO₂ measurements areabove or equal to the first threshold, and administering an interventionof level-N if any of the first plurality of SpO₂ measurements is below afirst threshold, where N is an integer and N has a value of 1 orgreater. In an aspect, the incidence of ulcers in patients in the carefacility is reduced to less than 1 in 100, less than 1 in 200, less than1 in 300, less than 1 in 400, less than 1 in 500, less than 1 in 600,less than 1 in 700, less than 1 in 800, less than 1 in 900, or less than1 in 1000.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a barrier cream to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold. In an aspect,a plurality of perfusion measurements are made at least once every houror at least once every half an hour if the delta value exceeds thethreshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every two hours if any of the pluralityof SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's heel, the method comprisingthe steps of: making a plurality of perfusion measurements at thepatient's heel, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'sheel if the delta value exceeds the threshold, and making a plurality ofperfusion measurements every hour if the delta value exceeds thethreshold. In an aspect, a plurality of perfusion measurements are madeat least once every half an hour if the delta value exceeds thethreshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's heel, the method comprisingthe steps of: making a plurality of SpO₂ measurements at the patient'sheel, determining whether any of the plurality of SpO₂ measurements isbelow a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'sheel if any of the plurality of SpO₂ measurements is below thethreshold, and making a plurality of SpO₂ measurements every hour if anyof the plurality of SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a topical cream to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery half an hour if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every half an hour if any of theplurality of SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aheel boot to the patient's heel, the method comprising the steps of:making a plurality of perfusion measurements at the patient's heel,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a heel boot to the patient's heel if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery half an hour if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aheel boot to the patient's heel, the method comprising the steps of:making a plurality of SpO₂ measurements at the patient's heel,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a heel boot to the patient's heel if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every half an hour if any of theplurality of SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's sacrum, the method comprising the stepsof: making a plurality of perfusion measurements at the patient'ssacrum, calculating a delta value from a portion of the plurality ofperfusion measurements, determining whether the delta value exceeds athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's sacrum if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every six hours if the delta value exceeds the threshold.In an aspect, a plurality of perfusion measurements are made at leastonce every four hours, at least once every three hours, at least onceevery two hours, at least once an hour, or at least once every half anhour if the delta value exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of abarrier cream to the patient's sacrum, the method comprising the stepsof: making a plurality of SpO₂ measurements at the patient's sacrum,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a barrier cream to the patient's sacrum if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every six hours if any of the pluralityof SpO₂ measurements is below the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's sacrum, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's sacrum, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a neuro-muscular stimulation to the patient'ssacrum if the delta value exceeds the threshold, and making a pluralityof perfusion measurements every four hours if the delta value exceedsthe threshold. In an aspect, a plurality of perfusion measurements aremade at least once every three hours, at least once every two hours, atleast once an hour, or at least once every half an hour if the deltavalue exceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of aneuro-muscular stimulation to the patient's sacrum, the methodcomprising the steps of: making a plurality of SpO₂ measurements at thepatient's sacrum, determining whether any of the plurality of SpO₂measurements is below a threshold corresponding to level N, where N isgreater than or equal to 2, administering a neuro-muscular stimulationto the patient's sacrum if any of the plurality of SpO₂ measurements isbelow the threshold, and making a plurality of SpO₂ measurements everyfour hours if any of the plurality of SpO₂ measurements is below thethreshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's sacrum, the method comprising the stepsof: making a plurality of perfusion measurements at the patient'ssacrum, calculating a delta value from a portion of the plurality ofperfusion measurements, determining whether the delta value exceeds athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's sacrum if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.In an aspect, a plurality of perfusion measurements are made at leastonce an hour or at least once every half an hour if the delta valueexceeds the threshold.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of atopical cream to the patient's sacrum, the method comprising the stepsof: making a plurality of SpO₂ measurements at the patient's sacrum,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a topical cream to the patient's sacrum if any of theplurality of SpO₂ measurements is below the threshold, and making aplurality of SpO₂ measurements every two hours if any of the pluralityof SpO₂ measurements is below the threshold.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application oftherapeutic ultrasound, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering therapeutic ultrasound to the anatomic site if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.In an aspect, an anatomical site is selected from the group consistingof a sternum, a sacrum, a heel, a scapula, an elbow, an ear, and otherfleshy tissues over a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application oftherapeutic ultrasound, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering therapeutic ultrasound to the anatomic site if any ofthe plurality of SpO₂ measurements is below the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application ofshockwave therapy, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering shockwave therapy to the anatomic site if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient. In one aspect, shockwave therapy isprovided via electromagnetic pulse or pressurized air.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application ofshockwave therapy, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering shockwave therapy to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient. In one aspect, shockwave therapy isprovided via electromagnetic pulse or pressurized air.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of a30-degree wedge, the method comprising the steps of: making a pluralityof perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a 30-degree wedge to the anatomic site if the delta valueexceeds the threshold, and making a plurality of perfusion measurementsevery two hours if the delta value exceeds the threshold. In an aspect,an anatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of a30-degree wedge, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a 30-degree wedge to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of acomposite dressing, the method comprising the steps of: making aplurality of perfusion measurements at an anatomic site of the patient,calculating a delta value from a portion of the plurality of perfusionmeasurements, determining whether the delta value exceeds a thresholdcorresponding to level N, where N is greater than or equal to 2,administering a composite dressing to the anatomic site if the deltavalue exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.In an aspect, an anatomical site is selected from the group consistingof a sternum, a sacrum, a heel, a scapula, an elbow, an ear, and otherfleshy tissues over a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of acomposite dressing, the method comprising the steps of: making aplurality of SpO₂ measurements at an anatomic site of the patient,determining whether any of the plurality of SpO₂ measurements is below athreshold corresponding to level N, where N is greater than or equal to2, administering a composite dressing to the anatomic site if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of a hybridmattress, the method comprising the steps of: making a plurality ofperfusion measurements at an anatomic site of the patient, calculating adelta value from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a threshold corresponding tolevel N, where N is greater than or equal to 2, providing a hybridmattress to support the patient if the delta value exceeds thethreshold, and making a plurality of perfusion measurements every twohours if the delta value exceeds the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of ahybrid mattress, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,providing a hybrid mattress to support the patient if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In one aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of a dynamicmattress, the method comprising the steps of: making a plurality ofperfusion measurements at an anatomic site of the patient, calculating adelta value from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a threshold corresponding tolevel N, where N is greater than or equal to 2, providing a dynamicmattress to support the patient if the delta value exceeds thethreshold, and making a plurality of perfusion measurements every twohours if the delta value exceeds the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and treating a patient in need of application of adynamic mattress, the method comprising the steps of: making a pluralityof SpO₂ measurements at an anatomic site of the patient, determiningwhether any of the plurality of SpO₂ measurements is below a thresholdcorresponding to level N, where N is greater than or equal to 2,providing a dynamic mattress to support the patient if any of theplurality of SpO₂ measurements is below the threshold. In an aspect, ananatomical site is selected from the group consisting of a sternum, asacrum, a heel, a scapula, an elbow, an ear, and other fleshy tissuesover a bony prominence of a patient.

In an aspect, the present disclosure provides for, and includes, amethod of identifying and moving a bedridden patient in need thereof,the method comprising the steps of: providing a mobility sensorcomprising an accelerometer and a gyro sensor; monitor frequency andrange of mobilization of the patient; providing an alert when themobility sensor does not sense a movement more than a quarter turn for aspecified period of time; and moving the patient upon the alert.

In an aspect, the present disclosure further provides for, and includes,providing targeted treatment to an anatomical location of a patientidentified as being damaged by a combination of a visual assessment andperfusion measurements. In one aspect, a targeted treatment is providedto a common site for wound development selected from the groupconsisting of: toes, heels, a sacrum, a spine, elbows, shoulder blades,occiput, and ischial tuberosity. In an aspect, a targeted treatment isconcurrently provided to a second common site for wound developmentselected from the group consisting of: toes, heels, a sacrum, a spine,elbows, shoulder blades, occiput, and ischial tuberosity. In one aspect,a first site receiving a targeted treatment is known to cause adevelopment of a wound at a second site.

Comparison of Bisymmetric Perfusion Measurements to Identify DamagedTissue

FIG. 22A depicts the sacral region of the back of a patient 1910. A lineof symmetry 1912 can be drawn down the center of the back, dividing theback into left and right mirror images. Locations 1914 are approximatelythe same distance from line of symmetry 1912 and approximately at thesame height and are, therefore, considered to be bisymmetric locationson the back of patient 1910.

FIG. 22B depicts left foot 20L and right foot 20R of a patient 10, asseen if patient 10 were lying on the back on a bed (not shown) and anobserver were standing at the foot of the bed. With respect to soles 22Land 22R of feet 20L and 20R, locations 24L and 24R are located atapproximately equivalent locations, e.g. the same distance from theposterior surface, i.e. the heel, and the same distance from the medialside of respective foot 20L or 20R and are considered to be bisymmetriclocations.

FIG. 22C depicts additional exemplary bisymmetric locations 26L and 26Rlocated on the lateral sides of feet 20L and 20R, and bisymmetriclocations 28L and 28R located on respective soles 22L and 22R of feet20L and 20R. In an aspect, locations 26R and 30R are consideredbisymmetric with respect to foot 20R when considered alone withoutreference to foot 20L.

Without being limited to a particular theory, comparison of perfusionmeasurements taken at bisymmetric locations can compensate for an offsetof readings of a particular patient from a population of patients. Forexample, a patient may be dehydrated on a particular day whenmeasurements are being made. A comparison of the perfusion value ofhealthy tissue from the same patient, while in a dehydrated condition,may be shifted from the perfusion value of the same tissue at the samelocation when the patient is fully hydrated. If the tissue at onelocation is healthy while the tissue at the bisymmetric location isdamaged, a comparison of the readings taken at the bisymmetric locationswill exclude the “common mode” effect of dehydration variation at bothlocations and provide a more robust indication that tissue is damaged atone location.

A perfusion measurement apparatus 400 as provided in FIG. 4 may be usedto take measurements at multiple locations, for example a firstmeasurement at a first location and a second measurement at a secondlocation that is bisymmetric relative to the first location. In anaspect, apparatus 400 comprises a processor that can be configured byinstructions stored on a non-transitory computer-readable medium todetermine a characteristic of the measurements taken at multiplelocations or parameters associated with or derived from themeasurements, for example one or more of a difference between, anaverage of, or a difference of each from a common average of perfusionvalues respectively derived from multiple measurements. In one aspect,apparatus 400 comprises a display configured to show one or moreparameters associated with the measurements, for example a delta betweenperfusion values derived from measurements taken at two bisymmetriclocations.

In an aspect, apparatus 400 takes the measurements with two receivers430A and 430B essentially simultaneously. In one aspect, apparatus 400takes the measurements in sequence with a time interval between themeasurements that ranges from zero to one second or more. In an aspect,a measurement by apparatus 400 is triggered by actuation of a button oran actuator. In one aspect, a measurement by apparatus 400 is triggeredautomatically based on input from a switching element that is part ofapparatus 400, for example a contact sensor, a pressure sensor, anoptical sensor, or other type of proximity-detecting device that ispositioned, in an aspect, proximate to one or more of receivers 430A and430B. In one aspect, multiple switching elements have to besimultaneously activated to provide the input to take the measurement.In an aspect, apparatus 400 comprises a processor that is coupled to acircuit and receives information about measured reflected light from thecircuit. In one aspect, information is in the form of an analog signal,e.g., an electrical voltage, or a digital signal. In an aspect, aprocessor is coupled directly to a plurality of receivers and isconfigured to measure reflected light directly. In one aspect, aprocessor is configured to convert the plurality of received reflectedlight measurement into a plurality of perfusion values. In an aspect, aprocessor is configured by machine-readable instructions that are storedon a non-transitory, computer-readable medium that is electronicallycoupled to the processor. In one aspect, instructions are loaded from amedium into a processor when apparatus 400 is powered on.

In an aspect, a measured reflected light parameter is related to theperfusion of blood in the epidermis of a patient at a depth that isdetermined by the spatial geometry of receivers 430A and 430B, thewavelength or wavelengths of light emitted by emitter 420, and otheroperating characteristics of apparatus 400. In one aspect, the magnitudeof reflected light detected by a receiver 430 is equivalent to theperfusion with a value on a predetermined scale. In an aspect, apredetermined scale may range from 0 to 20, such as from 0 to 1, from 0to 2, from 0 to 3, from 0 to 4, from 0 to 5, from 0 to 6, from 0 to 7,from 0 to 8, from 0 to 9, from 0 to 10, from 0 to 11, from 0 to 12, from0 to 13, from 0 to 14, from 0 to 15, from 0 to 16, from 0 to 17, from 0to 18, from 0 to 19. In one aspect, a predetermined scale can be scaledby a factor or a multiple based on the values provided herein. In anaspect, multiple measurements are taken while varying one or more ofoperating characteristics between readings, thereby providinginformation related to the perfusion at various depths of the skin.

In one aspect, a difference between perfusion values is determined,where a difference that exceeds a predetermined threshold is indicativeof tissue damage at one of the locations where the correspondingperfusion measurements were taken. In an aspect, means of perfusionvalues obtained at each bisymmetric locations are determined andcompared. In one aspect, medians or modes of perfusion values obtainedat each bisymmetric locations are determined and compared. In an aspect,the damage is indicated to be at the location associated with the largerof the perfusion values. In one aspect, the damage is indicated to be atthe location associated with the smaller of the perfusion values. In anaspect, determination of whether there is tissue damage comprises one ormore of comparison of individual perfusion values with one or morepredetermined ranges or thresholds and comparison of the difference withone or more predetermined ranges or thresholds. In an aspect, apredetermined range may be from 0.1 to 8.0, such as from 0.1 to 1.0,from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0, from 4.1 to 5.0, from5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from 0.1 to 7.5, from 0.5to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0 to 6.0, from 3.0 to5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In an aspect, a predeterminedrange may be from 0.1 to 4.0, such as from 0.5 to 4.0, from 0.1 to 3.5,from 1.0 to 3.5, from 1.5 to 4.0, from 1.5 to 3.5, from 2.0 to 4.0, from2.5 to 3.5, from 2.0 to 3.0, from 2.0 to 2.5, or from 2.5 to 3.0. In oneaspect, a predetermined range may be from 4.1 to 8.0, such as from 4.5to 8.0, from 4.1 to 7.5, from 5.0 to 7.5, from 5.5 to 7.0, from 5.5 to7.5, from 6.0 to 8.0, from 6.5 to 7.5, from 6.0 to 7.0, from 6.0 to 6.5,or from 6.5 to 7.0. In one aspect, a predetermined threshold may beabout 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85,0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1,2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5,3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9,5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3,6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In oneaspect, a predetermined threshold may range from 0.1 to 8.0, such asfrom 0.1 to 1.0, from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0, from4.1 to 5.0, from 5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from 0.1to 7.5, from 0.5 to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0 to6.0, from 3.0 to 5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In an aspect,a predetermined range or threshold can be scaled by a factor or amultiple based on the values provided herein. It will be understood thata predetermined value is not limited by design, but rather, one ofordinary skill in the art would be capable of choosing a predeterminedvalue based on a given unit of perfusion. In one aspect, ranges andthresholds of the present disclosure are varied according to thespecific bisymmetric locations, the portion of a patient's body on whichmeasurements are being made, or one or more characteristics of thepatient such as age, height, weight, family history, ethnic group, andother physical characteristics or medical conditions.

One or more regions may be defined on a body. In an aspect, measurementsmade within a region are considered comparable to each other. A regionmay be defined as an area on the skin of the body wherein measurementsmay be taken at any point within the area. In an aspect, a regioncorresponds to an anatomical region (e.g., heel, ankle, lower back). Inan aspect, a region may be defined as a set of two or more specificpoints relative to anatomical features wherein measurements are takenonly at the specific points. In an aspect, a region may comprise aplurality of non-contiguous areas on the body. In an aspect, the set ofspecific locations may include points in multiple non-contiguous areas.

In an aspect, a region is defined by surface area. In an aspect, aregion may be, for example, between 5 and 200 cm², between 5 and 100cm², between 5 and 50 cm², or between 10 and 50 cm², between 10 and 25cm², or between 5 and 25 cm².

In an aspect, measurements may be made in a specific pattern or portionthereof. In an aspect, the pattern of readings is made in a pattern withthe target area of concern in the center. In an aspect, measurements aremade in one or more circular patterns of increasing or decreasing size,T-shaped patterns, a set of specific locations, or randomly across atissue or region. In an aspect, a pattern may be located on the body bydefining a first measurement location of the pattern with respect to ananatomical feature with the remaining measurement locations of thepattern defined as offsets from the first measurement position.

In an aspect, a plurality of measurements are taken across a tissue orregion and the difference between the lowest measurement value and thehighest measurement value of the plurality of measurements is recordedas a delta value of that plurality of measurements. In an aspect, 3 ormore, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more,or 10 or more measurements are taken across a tissue or region.

In an aspect, a threshold may be established for at least one region. Inan aspect, a threshold of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, orother value may be established for the at least one region. In anaspect, a delta value is identified as significant when the delta valueof a plurality of measurements taken within a region meets or exceeds athreshold associated with that region. In an aspect, each of a pluralityof regions has a different threshold. In an aspect, two or more regionsmay have a common threshold.

In an aspect, a threshold has both a delta value component and achronological component, wherein a delta value is identified assignificant when the delta value is greater than a predeterminednumerical value for a predetermined portion of a time interval. In anaspect, the predetermined portion of a time interval is defined as aminimum of X days wherein a plurality of measurements taken that dayproduces a delta value greater than or equal to the predeterminednumerical value within a total of Y contiguous days of measurement. Inan aspect, the predetermined portion of a time interval may be definedas 1, 2, 3, 4, or 5 consecutive days on which a plurality ofmeasurements taken that day produces a delta value that is greater thanor equal to the predetermined numerical value. In an aspect, thepredetermined portion of a time interval may be defined as some portionof a different specific time period (weeks, month, hours etc.).

In an aspect, a threshold has a trending aspect wherein changes in thedelta values of consecutive pluralities of measurements are compared toeach other. In an aspect, a trending threshold is defined as apredetermined change in delta value over a predetermined length of time,wherein a determination that the threshold has been met or exceeded issignificant. In an aspect, a determination of significance will cause analert to be issued. In an aspect, a trend line may be computed from aportion of the individual measurements of the consecutive pluralities ofmeasurements. In an aspect, a trend line may be computed from a portionof the delta values of the consecutive pluralities of measurements.

In an aspect, the number of measurements taken within a single regionmay be less than the number of measurement locations defined in apattern. In an aspect, a delta value will be calculated after apredetermined initial number of readings, which is less than the numberof measurement locations defined in a pattern, have been taken in aregion and after each additional reading in the same region, whereinadditional readings are not taken once the delta value meets or exceedsthe threshold associated with that region.

In an aspect, the number of measurements taken within a single regionmay exceed the number of measurement locations defined in a pattern. Inan aspect, a delta value will be calculated after each additionalreading.

In an aspect, a quality metric may be generated for each plurality ofmeasurements. In an aspect, this quality metric is chosen to assess therepeatability of the measurements. In an aspect, this quality metric ischosen to assess the skill of the clinician that took the measurements.In an aspect, the quality metric may include one or more statisticalparameters, for example an average, a mean, or a standard deviation. Inan aspect, the quality metric may include one or more of a comparison ofindividual measurements to a predefined range. In an aspect, the qualitymetric may include comparison of the individual measurements to apattern of values, for example comparison of the measurement values atpredefined locations to ranges associated with each predefined location.In an aspect, the quality metric may include determination of whichmeasurements are made over healthy tissue and one or more evaluations ofconsistency within this subset of “healthy” measurements, for example arange, a standard deviation, or other parameter.

In an aspect, apparatus 400 is capable of storing multiple measurementand computation results. In one aspect, an apparatus in accordance withthe present disclosure may also comprise other components, for example abarcode scanner, and may be capable of storing the output of thatcomponent. In an aspect, apparatus 400 comprises components to transferthe stored data, for example via a Bluetooth, WiFi, or Ethernetconnection, to another device, for example a personal computer, server,tablet, or smart phone such as depicted in FIG. 13 .

In an aspect, apparatus 400 comprises two receivers 430A and 430B whichare located at separate locations on the apparatus body. An exampleusage would be to place apparatus 400 against a patient's body so as tosimultaneously position first receiver 430A at a first body location,and position second receiver 430B at a second body location, where bothbody locations are on the surface of a patient's skin. In an aspect, theapparatus body is rigid and maintains receivers 430A and 430B at a fixedseparation distance and fixed orientation to each other. In an aspect,receivers 430A and 430B are aligned on a common plane.

In an aspect, the apparatus body of apparatus 400 is flexible such thatreceivers 430A and 430B may be oriented at an angle to each other. In anaspect, one or more of receivers 430 are movable such that the anglebetween a movable receiver and the other receiver may be varied, forexample to match the orientation of the skin. In an aspect, bothreceivers are movable In an aspect, all receivers are movable. In anaspect, apparatus 400 comprises a hinge such the separation distancebetween receivers 430A and 430B may be varied. In an aspect, theapparatus body of apparatus 400 is rigid such that the angle and theseparation distance between the receivers are immovable.

In an aspect, apparatus 400 comprises a plurality of emitters 420 and aplurality of receivers 430 to form a planar array. In an aspect, theplanar array may take the form of a mat on which emitters 420 andreceivers 430 are disposed. In one aspect, the emitters 420 andreceivers 430 are embedded within the mat. In an aspect, the emitters420 and receivers 430 are located on the top surface the mat. In anaspect, the emitters 420 and receivers 430 have a cover layer over them.In an aspect, the emitters 420 are of a single type and configurationwithin the array. In an aspect, the receivers 430 are of a single typeand configuration within the array. In an aspect, the emitters 420 varyin size and type within the array. In an aspect, the receivers 430 varyin size and type within the array. In an aspect, the emitters 420 andreceivers 430 of the array are disposed in a regular geometric pattern,such as a grid-like pattern. In an aspect, the emitters 420 andreceivers 430 of the array are disposed in an irregular pattern. In anaspect, the mat is coupled to an electronics assembly either directly orthrough a cable. In one aspect, an electronics assembly comprises acircuit coupled to receivers 430 and a processor is coupled to thecircuit. In an aspect, the mat comprises one or more of pressuresensors, temperature sensors, optical sensors, and contact sensorsdisposed at one or more respective locations across the mat. In oneaspect, one or more measurements using receivers 430 are triggered byinput from one or more of the pressure, temperature, optical, andcontact sensors. In an aspect, the mat is configured as a floor mat andactuation of one or more of the pressure, temperature, optical, andcontact sensors, for example detection of a person standing on the matdue to detection of the weight of a person by a pressure sensor,initiates a measurement by one or more of receivers 430. In one aspect,receivers 430 are operated in a “detection mode” that is capable ofdetecting when a person steps onto mat and transitions into a“measurement mode” upon determination that a person is standing on themat. In an aspect, the mat is configured as a portable apparatus thatcan be placed against a surface of a patient's skin, for example againsta patient's back or against the soles of one or both of their feet whilethe patient is lying in bed. In one aspect, the mat comprises one ormore of a support tray, stiffening element, and conformal pad to aid inplacing receivers 430 against a surface of a patient's skin.

In an aspect, two emitters may overlap 0-50%, such as 0-10%, 5-15%,10-20%, 15-25%, 20-30%, 25-35%, 30-40%, 35%-45%, 40-50%, 0-25%, 15-35%,or 25-50%. In one aspect, two emitters may overlap 25-75%, such as25-35%, 30-40%, 35%-45%, 40-50% 45-55%, 50-60%, 55-65%, 60-70%, 65-75%,25-50%, 40-55%, or 50-75%. In one aspect, two emitters may overlap50-100%, such as 50-60%, 55-65%, 60-70%, 65-75%, 70-80%, 75%-85%,80-90%, 85-95%, 90-100%, 50-75%, 65-85%, or 75-100%.

In an aspect, two receivers may overlap 0-50%, such as 0-10%, 5-15%,10-20%, 15-25%, 20-30%, 25-35%, 30-40%, 35%-45%, 40-50%, 0-25%, 15-35%,or 25-50%. In one aspect, two receivers may overlap 25-75%, such as25-35%, 30-40%, 35%-45%, 40-50% 45-55%, 50-60%, 55-65%, 60-70%, 65-75%,25-50%, 40-55%, or 50-75%. In one aspect, two receivers may overlap50-100%, such as 50-60%, 55-65%, 60-70%, 65-75%, 70-80%, 75%-85%,80-90%, 85-95%, 90-100%, 50-75%, 65-85%, or 75-100%.

In one aspect, the planar array of may further comprise a plurality ofcontact sensors on the same planar surface as, and surrounding, each ofthe receivers to ensure complete contact of each of the emitters andreceivers to the skin surface. The plurality of contact sensors may be aplurality of pressure sensors, a plurality of light sensors, a pluralityof temperature sensors, a plurality of pH sensors, a plurality ofperspiration sensors, a plurality of ultrasonic sensors, a plurality ofbone growth stimulator sensors, or a plurality of a combination of thesesensors. In an aspect, the plurality of contact sensors may comprisefour, five, six, seven, eight, nine, or ten or more contact sensorssurrounding each emitter or receiver.

FIGS. 23A and 23B depict an example of how comparison of perfusionvalues associated with receivers in known relative locations canidentify bisymmetric locations, according to the present disclosure. Inthis example, a receiver 430 is presented at non-overlapping locations,marked “A” to “H” in FIG. 23A, across a contact area 2050R of a rightfoot 20R. The perfusion values measured at each location are plotted inthe graph of FIG. 23B. In this example, the perfusion value of locations“A” and “H” are low or zero, reflecting the non-overlap of the receiver430 with contact area 2050R in those locations. The perfusion valuesassociated with locations “B” and “G” are higher, as the receiver 430overlaps a portion of contact area 2050R in those positions. Theperfusion values for locations C-D-E-F are higher and, in this example,approximately the same, indicating that the receiver 430 is completelywithin contact area 2050R at those locations. In one aspect, a perfusionmeasurement apparatus such as apparatus 400 may determine that certainlocations, for example locations “C” and “F,” are bisymmetric withrespect to a centerline 2052R of right foot 20R. In an aspect, where asimilar set of measurements is made at locations A′-H′ on left foot 20L,a location on each foot 20L and 20R, for example locations E and E′, maybe determined to be approximately bisymmetric.

FIG. 24 depicts a schematic depiction of an integrated system 2100 formeasurement, evaluation, storage, and transfer of perfusion values,according to the present disclosure. In this example, system 2100comprises a perfusion measurement apparatus 400, as discussed withrespect to FIG. 4 , that comprises the capability to wirelesslycommunicate with a WiFi access point 2110. Apparatus 400 communicateswith one or more of a perfusion application running on a server 2140, anapplication running on a laptop computer 2120, a smart phone 2130, orother digital device. In one aspect, laptop computer 2120 and smartphone 2130 are carried by a user of apparatus 400, for example a nurse,and an application provides feedback and information to the user. In anaspect, information received from apparatus 400 for a patient is storedin a database 2150. In one aspect, information received from apparatus400 is transferred over a network 2145 to another server 2160 thatstores a portion of information in an electronic medical record (EMR)2170 of a patient. In one aspect, information from apparatus 400 orretrieved from database 2150 or EMR 2170 is transferred to an externalserver 2180 and then to a computer 2185, for example a computer at theoffice of a doctor who is providing care for a patient.

Perfusion Measurement Trend Analysis to Detect Tissue Damage

FIG. 25 depicts perfusion values over time for patients who are at riskof developing pressure ulcers, in accordance with the presentdisclosure. In an aspect, a perfusion value is a single perfusionmeasurement. In an aspect, a perfusion value is an average perfusionmeasurement generated from perfusion measurement values taken atapproximately the same location on a patient's skin within a 24-hourperiod, such as within a 18-hour period, within a 12-hour period, withina 8-hour period, within a 6-hour period, within a 4-hour period, withina 3-hour period, within a 2-hour period, within an hour, within 45minutes, within 30 minutes, within 15 minutes, within 10 minutes, within5 minutes, within 1 minute, or within 30 seconds.

Curve 2210 represents average perfusion values for a set of patientshaving a high risk of developing pressure ulcers over the days leadingup to the development of a pressure ulcer on Day 0. The overlaidstraight line is a linear approximation. Curve 2220 represents averageperfusion values for a set of patients having a low risk of developingpressure ulcers over the days leading up to Day 0, where no pressureulcer develops on Day 0. In both cases, there was no sign of damage orindication of a future pressure ulcer on the skin. The perfusion valueswere indicative of subsurface damage that was invisible to visual andtactile examination (e.g. change in elasticity or temperature). Theoverlaid straight line is a linear approximation.

FIG. 26 depicts perfusion delta values over time for patients thatdevelop pressure ulcers, in accordance with the present disclosure.Curves 2302 and 2304 illustrate the acceleration of the rate ofincrease, i.e. the slope, of the curve as time gets closer to the pointat which a visual examination leads to a clinical diagnosis. Curve 2310is an average of the other curves and shows the upward curve, i.e.acceleration of the rate of increase.

FIG. 27 is an example plot of measured and computed perfusion values, inaccordance with the present disclosure. Curve 2410 is a set of perfusionvalues for a skin area that is prone to development of a pressure ulcer.Curve 2420 is a matching set of perfusion values for a second skin areathat is near the first area but not at risk for a pressure ulcer. Curve2420 serves as a reference. Curve 2430 is a “delta” perfusion valuecalculated by subtracting the reference value of curve 2420 from thematching perfusion value of curve 2410.

Tissue damage may be detected in several ways. In one aspect, the slopeof the perfusion curve 2410, for example the slope between points 2414and 2416, is compared against a threshold slope, indicated by line 2412.If the slope of the curve 2410 exceeds the slope of line 2412, thisindicates a degree of damage. There may be multiple slopes used toevaluate multiple degrees of tissue damage. In one aspect, a slope isdetermined with respect to any two points on perfusion curve 2410, andis compared to the slope of line 2412 to indicate a degree of damage. Inan aspect, a slope is determined by taking the derivative of theperfusion curve 2410. In an aspect, the slope of line 2412 is determinedby the health history of the subject. In one aspect, the curvature of aperfusion curve is compared to a threshold curvature, where anover-curvature indicates a degree of damage.

In an aspect, tissue damage may be detected before it is visible on apatient's skin by: measuring a plurality of SpO₂ values at a singlelocation at incremental times, calculating a slope between the latestSpO₂ value and the immediately prior SpO₂ value, comparing this slope toa threshold value, and determining that there is tissue damage if theslope exceeds the threshold value.

In an aspect, tissue damage may be detected before it is visible on apatient's skin by: measuring a plurality of SpO₂ values at a singlelocation at incremental times, calculating a derivative between thelatest SpO₂ value and the immediately prior SpO₂ value, comparing thisderivative to a threshold value, and determining that there is tissuedamage if the derivative exceeds the threshold value.

In an aspect, the value of the delta curve 2430 is compared to athreshold level 2438. When curve 2430 exceeds threshold 2438, forexample at point 2436, this indicates a degree of damage. There may bemultiple thresholds used to evaluate multiple levels of tissue damage.

In an aspect, tissue damage may be detected before it is visible on apatient's skin by: measuring a plurality of SpO₂ values at a singlelocation at each of a plurality of incremental times, calculating anaverage value for each incremental time, fitting a curve to apredetermined number of the most-recent SpO₂ average values, calculatinga curvature of the fitted curve, comparing this curvature to a thresholdvalue, and determining that there is tissue damage if the curvatureexceeds the threshold value.

In an aspect, a threshold may be about 0.3, 0.35, 0.4, 0.45, 0.5, 0.55,0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4,1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8,2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2,4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6,5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0,7.1, 7.2, 7.3, 7.4, or 7.5. In one aspect, a threshold may range from0.1 to 8.0, such as from 0.1 to 1.0, from 1.1 to 2.0, from 2.1 to 3.0,from 3.1 to 4.0, from 4.1 to 5.0, from 5.1 to 6.0, from 6.1 to 7.0, from7.1 to 8.0, from 0.1 to 7.5, from 0.5 to 8.0, from 1.0 to 7.0, from 1.5to 6.5, from 2.0 to 6.0, from 3.0 to 5.5, from 3.5 to 5.0, or from 4.0to 4.5. In an aspect, a threshold can be scaled by a factor or amultiple based on the values provided herein. It will be understood thata threshold is not limited by design, but rather, one of ordinary skillin the art would be capable of choosing a predetermined value based on agiven unit of perfusion. In one aspect, thresholds of the presentdisclosure are varied according to the specific portion of a patient'sbody on which measurements are being made, or one or morecharacteristics of the patient such as age, height, weight, familyhistory, ethnic group, and other physical characteristics or medicalconditions.

In one aspect, the slope of the delta curve 2430, for example the slopebetween points 2434 and 2436, is compared against a threshold slope,indicated by line 2432. If the slope of the curve 2430 exceeds the slopeof line 2432, this indicates a degree of damage. There may be multipleslopes used to evaluate multiple degrees of tissue damage. In oneaspect, a slope is determined with respect to any two points on deltacurve 2430, and is compared to the slope of line 2432 to indicate adegree of damage. In an aspect, the slope of line 2432 is determined bythe health history of the subject. In one aspect, the curvature of adelta curve is compared to a threshold curvature, where anover-curvature indicates a degree of damage.

In an aspect, a perfusion delta value above a predefined threshold valueis an indication of sub-epidermal damage that may lead to a pressureulcer. The time interval between the time when the perfusion delta valuefirst equals or exceeds this threshold and the development of visiblesymptoms of a pressure ulcer may be a first duration when the perfusiondelta value increases linearly. A first duration may be 5 or more days,such as 6 or more days, 7 or more days, 8 or more days, 9 or more days,or 10 or more days.

In another aspect, when the perfusion delta curve shows an upwardcurvature or other deviation above a linear progression, the visiblesymptoms may be present within a shorter amount of time, for example 2-3days, 1-4 days. 1-3 days, 1-2 days, or 2-4 days. In an aspect, theperfusion measurement apparatus 400, which includes a receiver 430 andelectronics to measure reflected light and convert this reflected lightmeasurement to a perfusion value and store a plurality of theseperfusion values then calculate and display a perfusion delta value fromthe plurality of perfusion values and transmit a portion of themeasurements and delta values to a remote computer, is used to generatea perfusion delta value for a particular location on the patient's skin,for example the heel. These perfusion delta values are tracked and thetrend of the perfusion delta values, i.e. the slope and curvature of acurve connecting these perfusion delta values, is analyzed. In anaspect, the amount by which an incremental perfusion delta value isabove a linear prediction based on prior perfusion delta values iscompared to a predetermined threshold. In an aspect, the amount by whichan incremental perfusion delta value is above the most recent priorperfusion delta value is compared to a predetermined threshold. In anaspect, a curvature of the best-fit curve fitted to a predefined numberof the most-recent perfusion delta values is compared to a predeterminedthreshold. In an aspect, the number of sequential perfusion delta valuesthat exceeds a predetermined value threshold is compared to anumber-of-readings threshold. In each of these aspects, the perfusionscanner provides a notification when the comparison parameter exceedsthe respective threshold.

In an aspect, the trend analysis may ignore a single perfusion deltavalue that is below a threshold if both the prior and subsequentperfusion delta values are above the threshold.

In an aspect, the trend curve of the perfusion delta values is apoint-to-point linear connection. In an aspect, the trend curve is abest-fit curve fitted to the perfusion delta values. In an aspect, thefitted curve is required to intersection the most-recent perfusion deltavalue.

Having now generally described the invention, the same will be morereadily understood through reference to the following examples that areprovided by way of illustration, and are not intended to be limiting ofthe present disclosure, unless specified.

EXAMPLES Example 1: Intervention Levels for Treating Pressure Ulcers inthe Heel

Subjects identified as being at risk for pressure ulcers in the heel aretreated in accordance with the following scheme:

TABLE 1 EXAMPLE INTERVENTION SCHEME FOR TREATING A PRESSURE ULCER IN THEHEEL Frequency of Subsequent Corresponding Risk Perfusion MeasurementPerfusion Level Intervention Monitoring delta Ranges 0 provide goodnutrition, standard every 24 hours perfusion delta ≤ mattress, and/orturn every 24 hours threshold 1 provide a heel boot every 10 hoursthreshold < perfusion delta ≤ 105% threshold 2 change of support surfaceat the beginning of each 105% threshold < nursing shift perfusion delta≤ 110% threshold 3 apply dressing to back or sides of every 12 hours110% threshold < heel perfusion delta ≤ 115% threshold 4 change tolow-friction sheet cover every 8 hours 115% threshold < perfusion delta≤ 120% threshold 5 provide a low-friction padded every 6 hours 120%threshold < mattress surface for lower leg perfusion delta ≤ 125%threshold 6 turn patient at a shorter interval every 4 hours 125%threshold < perfusion delta ≤ 130% threshold 7 apply barrier cream every2 hours 130% threshold < perfusion delta ≤ 135% threshold 8 applyneuro-muscular stimulation every 1 hour 135% threshold < perfusion delta≤ 145% threshold 9 apply topical cream to enhance every 30 minutes 145%threshold < perfusion perfusion delta ≤ 150% threshold 10 providesilicone pad for lower leg every 15 minutes 150% threshold < perfusiondelta

Example 2: Intervention Levels for Treating Pressure Ulcers in theSacrum

Subjects identified as being at risk for pressure ulcers in the sacrumare treated in accordance with the following scheme:

TABLE 2 EXAMPLE INTERVENTION SCHEME FOR TREATING A PRESSURE ULCER IN THESACRUM Frequency of Subsequent Corresponding Risk Perfusion MeasurementPerfusion Level Intervention Monitoring delta Ranges 0 provide goodnutrition, standard every 24 hours perfusion delta ≤ mattress, and/orturn every 24 hours threshold 1 reposition patient with wedge and/orevery 10 hours threshold < keep sacrum dry perfusion delta ≤ 110%threshold 2 change mattress to pressure- at the beginning of each 110%threshold < alleviating mattresses nursing shift perfusion delta ≤ 120%threshold 3 apply dressing over sacrum every 12 hours 120% threshold <perfusion delta ≤ 130% threshold 4 change to dynamic mattress every 8hours 130% threshold < perfusion delta ≤ 140% threshold 5 apply barriercream every 6 hours 140% threshold < perfusion delta ≤ 150% threshold 6apply neuro-muscular stimulation every 4 hours 150% threshold <perfusion delta ≤ 160% threshold 7 apply topical cream to enhance every2 hours 160% threshold < perfusion perfusion delta ≤ 170% threshold 8provide silicone pad under the every 1 hour 170% threshold < patient'sbody perfusion delta ≤ 180% threshold

Example 3: Example Process for Selecting a Level of Intervention andMonitoring

FIG. 15 is an illustration of a process 1500 for selecting a level ofintervention and monitoring based on the amount by which a delta valuederived from perfusion measurements exceeds a threshold value. Here, acaregiver takes a plurality of perfusion measurements at a location onthe skin of a patient in step 1502, where each measurement generates aperfusion value. Using a portion of these perfusion values, a deltavalue “Δ” is calculated in step 1504. The delta value is calculated bysubtracting the smallest perfusion value from the largest perfusionvalue generated from the plurality of perfusion measurements.

The calculated delta value is compared to a threshold value “T” in step1506. If the delta value is less than or equal to the threshold value,step 1508 is executed and the caregiver waits until the monitoringinterval associated with the current level of care transpires, thenrepeats the perfusion measurements in step 1502. If the delta value isgreater than the threshold value, the amount by which the delta valueexceeds the threshold value is compared to a cascading series ofdifference values.

In some instances, the delta value is positive and the comparisonexecuted by subtracting the threshold value from the delta value, whichproduced a positive difference, and then a determination is maderegarding whether the difference exceeded the first difference D1 instep 1510. If the difference is less than D1, the process branched tostep 1512 and then step 1514 to implement an intervention andmeasurement interval, respectively, associated with level-N+1. In thisexample, N has a value of zero or greater.

In some instances, the delta value is negative. In that case, thedifferences D1, D2 through Dn are selected to have negative values thatcan have different absolute values than the corresponding differencevalues D1, D2 through Dn used for a positive delta value. Alternatively,the comparisons in steps 1510, 1520, and 1530 are changed to “≤” inplace of the “≥” shown in FIG. 15 .

Example 4: Workflow Guidance Matrix

FIG. 16 is an example of a workflow guidance matrix 1600 where thecurrent level of intervention 1602 and the new delta value 1604 are usedto select the new level of intervention 1606. Here, a caregiver monitorsthe condition of a patient by periodically taking a plurality ofperfusion measurements at one or more locations on the patient's skin.At the time of these measurements, the patient receives care associatedwith a level of intervention and monitoring. In this example, level-0(zero) is associated with a patient who was not considered to be atsignificant risk for development of tissue damage. Higher levels ofintervention and monitoring are identified with the gradations ofintervention ranked, for example, according to cost, difficulty toimplement, or other parameter identified by the care facility. When acaregiver is making a new set of perfusion measurements, they consultthis matrix by identifying the row of the current level of intervention1602, the delta value determined from the latest set of perfusionmeasurements 1604, and identifies the level of intervention in the cell1606 at the intersection of the row 1602 and column 1604. The caregivercan consider the identified level of intervention as well as the currentlevel of intervention and the value of the delta in selecting a level ofintervention for the next time period.

In some instances, the values of the new levels of intervention in thecells 1606 are similar from row to row. In some instances, the values ofthe new levels of intervention in adjacent cells 1606 differed by asingle level or by more than one level. In some instances, the values ofthe new levels of intervention in adjacent cells 1606 are the same inadjacent cells.

Example 5: Progression of Tissue Condition Leading to Development of aWound

FIG. 17 shows an illustrative plot 1700 of a delta value for a singlepatient at a single location where a wound develops. The perfusionvalues are measured by an apparatus of for assessing perfusion of bloodin tissue below a patient's skin. A delta value is generated from setsof perfusion measurements taken at incremental times. Point 1772 is ameasurement at time=zero where all the perfusion values had a baselinevalue associated with healthy tissue and the delta value is zero. Attime t1, another set of perfusion measurements is made and theassociated delta value is indicated at point 1774. This delta value isbelow the threshold 1762 and, therefore, there is no indication ofsignificant sub-surface damage.

At time t2, the damage progresses and the delta value 1776 is greaterthan the threshold 1762, indicating that there is significant damage.This damage is still not visible on the skin. Nonetheless, a delta valuegreater than the threshold 1762 indicates that there is cellular damageat a depth less than the sensitive depth of the perfusion measurementapparatus.

At time t3, the damage continues but the amount of fluid in theintercellular space is decreased due to mechanical expulsion. Thisreduced the perfusion value taken over the damaged area, which reducedthe computed delta value 1778 since the perfusion value of the healthytissue remains much the same as during previous measurements.

At time t4, the damage progresses to the point where it was visible onthe skin surface. In some instances, time t4 may occur before one orboth of t2 and t3. In some instances, time t4 may occur after the deltavalue has reached zero again along curve 1770 after time t3 and beforet5. Arrow 1765 indicates that after time t4, the damage remains visible.

At time t5, the damage progresses to the point where sufficient fluidhas been expelled from the local tissue that the perfusion value of ameasurement made over the damaged area is lower than the perfusion valueof healthy tissue. This results in the delta value 1780 being negative.In some instances, the negative delta would indicate that the tissue isseriously damaged. In some instances, the negative delta would indicatethat a portion of the tissue at the location of the lowest perfusionvalue is necrotic.

Example 6: Method of Mapping an Area of Possible Damage I

FIG. 18A is an example of a method of mapping an area of possibledamage. The area of damage 1800 is surrounded by healthy tissue 1808.The center area 1830 is significantly damaged. The first surroundingarea 1820 is less damaged, and the second surrounding area 1810 is lessdamaged but still not healthy tissue. The skin over all of these areashave the same appearance and texture, with no indication of thesubsurface damage. The series of dashed-line circles 1840, 1842, 1844,1846, 1848, and 1850 indicate an example set of location where perfusionmeasurements were taken. Perfusion measurements taken at locations 1840,1842, and 1850 generally produce a perfusion value associated withhealthy tissue, identified within this example as “H.” Perfusionmeasurements taken at locations 1844 and 1848 generally produce aperfusion value “J” that is slightly higher than H. A perfusionmeasurement taken at location 1846 generally produces a perfusion value“P” that is greater than J. All of these measurements are considered tobe taken at a single “location” on the patient's body, for example thesacrum, even though the individual locations are spatially dispersedover this location. For this set of perfusion values, the delta is thedifference between the highest perfusion value, which likely occurred atlocation 1846, and the lowest perfusion value, which likely occurred atone of locations 1840, 1842, and 1850, within this set. If the delta isgreater than a threshold value “T,” this is an indication that there issignificant damage at this location. The exact location of the greatestdamage is likely to be proximate to the measurement location 1846 wherethe greatest perfusion value is produced.

Example 7: Method of Mapping an Area of Possible Damage II

FIG. 18B depicts a second example of mapping an area of possible damage.In this example, the approximate location of the greatest damage isknown, for example from prior application of the method illustrated inFIG. 18A. The intent of this method is to map the boundary between area1810 and area 1820 to determine the extent of the damage. Forsimplicity, the perfusion values produced by measurements in each areawere the same and the perfusion values increased from area 1810 to area1820 and then to area 1830. The first perfusion measurement is taken atlocation 1860, which is known to be the approximate location of thegreatest damage. Subsequent measurements are taken at locations 1862,1864, 1866, and 1868 in the order indicated by path 1880. The perfusionvalue produced at location 1864 is slightly higher than the perfusionvalues produced at locations 1862 and 1866, indicating that location1864 was partially within the area 1820 while locations 1862 and 1866were fully within the lesser-damaged area 1810. The boundary can beapproximated by interpolating between the various measurement locations.For example, the perfusion value produced at location 1870 is highenough to suggest that it is fully within the area 1820 and thereforedoes not help identify the boundary between areas 1810 and 1820. Thesubsequent location 1872 is therefore directly away from the startinglocation 1860. As location 1860, in this example, is now fully withinarea 1810, the boundary between areas 1810 and 1820 can be interpolatedto be between locations 1870 and 1872. The perfusion value produced froma measurement at location 1874 is similar to the perfusion value fromlocation 1870 and it can be sufficient to identify the boundary asoutside the location 1874 without taking another measurement at alocation corresponding to location 1872.

This set of measurements enable the creation of a map of a certain levelof damage, for example the area 1820. Repeating this mapping process atregular time intervals would provide an indication of whether the area1820 is growing, which may indicate that an increased level ofintervention is appropriate, or shrinking, which may indicate that thecurrent level of intervention is allowing the damage to heal.

Example 8: Treatment Decision Pathway for Stratifying Patients andProviding Appropriate Treatments

FIG. 19A outlines a currently recommended treatment decision pathway forpreventing pressure ulcers in hospital patients as presented by TheNational Institute for Health and Care Excellence (NICE) in theirclinical guideline Pressure ulcers: prevention and management, published23 Apr. 2014. The guidelines recommend that a risk analysis be performedfor every patient admitted to a care facility that exhibits one or morerisk factors such as significantly limited mobility, a significant lossof sensation, a previous or current pressure ulcer, a nutritionaldeficiency, an inability to reposition themselves, or a significantcognitive impairment. Risk assessment is commonly done using a scoredchecklist, such as the Braden Scale, that assesses the severity ofspecific risk factors.

Upon completion of the risk assessment, the patient is identified as (i)having a low risk of developing a pressure ulcer, (ii) being at risk ofdeveloping a pressure ulcer, or (iii) being at high risk of developing apressure ulcer. Depending on the level of risk the patient is classifiedas having, the patient undergoes different sequences of treatment andevaluation by visual assessment.

All patients are potentially at risk of developing a pressure ulcer.They are more likely to occur in people who are seriously ill or have aneurological condition, impaired mobility, impaired nutrition, poorposture, or a deformity.

Pressure ulcers are categorized as stage-1 through stage-4, with stage-1being the lowest condition. The National Pressure Ulcer Advisory Panel(NPUAP) has defined a “stage-1” ulcer as intact skin with a localizedarea of non-blanchable erythema, where “blanchable” indicates that thetissue loses all redness when pressed and “non-blanchable” tissueremains red when pressed due to the presence of red blood cells outsideof blood vessels (extravasation). In some patients, blanchable erythemaor changes in sensation, temperature, or firmness may precede visualchanges.

Visual skin assessment (VSA) is the current method of identifying apressure ulcer. A trained healthcare professional assesses theappearance of the skin, visually and tactilely, looking for redness orvariations in tissue firmness, tissue temperature, or moisture.

If a patient is identified as having a low risk of developing a pressureulcer, the patient is simply monitored for a change in clinical statussuch as undergoing surgery, worsening of an underlying condition, or achange in mobility. A patient who uses a wheelchair or sits forprolonged periods may be provided with a high-specification foam cushionor equivalent pressure-distributing cushion. If there is no change inclinical status, a low-risk patient will not be reassessed under thisset of guidelines and stays within the same treatment and evaluationpathway until he or she is discharged from the care facility.

If a patient is identified as being at risk of developing a pressureulcer, the patient will be scheduled to be turned, or “rounded,” every 6hours. As with the low-risk patient, a high-spec foam cushion may beprovided if the patient uses a wheelchair or sits for prolonged periodsof time. No other monitoring or intervention is recommended by the NICEguidelines.

A high-risk patient receives a high-spec foam mattress as a preventativemeasure, provided with a high-spec cushion if they are in a wheelchairor sit for prolonged periods of time, and will be turned every 4 hours.The patient will receive a daily VSA for all areas of the body. If anarea is found to have non-blanchable erythema, an appropriateintervention will be implemented and that area re-checked by VSA every 2hours. Areas that do not exhibit non-blanchable erythema are re-checkeddaily by VSA. A personalized care plan will be developed for eachhigh-risk patient.

It can be seen from this flow chart that the majority of the time spentby caregivers will be on the high-risk patients. While this may beappropriate, it leaves the at-risk patients unmonitored and they maydevelop a stage-1 ulcer before the condition is observed by a caregiver.Furthermore, the consequence of relying on VSA to detect a problemnecessarily means that patients will develop a stage-1 ulcer before anintervention is selected or implemented. By the time that the damage hasprogressed to stage-1, it is likely that the skin will break and becomea stage-2 ulcer despite intervention. There is a clear need to identifytissue damage earlier so that interventions can prevent progression ofthe subepidermal damage to stage-1 and beyond.

FIG. 19B is an example of a current augmented treatment decision pathwayfor preventing pressure ulcers as currently implemented at some healthcare facilities. The augmented pathway adds monitoring steps to both theat-risk and the low-risk paths. A low-risk patient received a weeklyrisk assessment, for example completion of the Braden Scale assessment.A patient identified as at-risk in the initial assessment will receive ahigh-spec foam mattress as a preventative measure and will be evaluateddaily by VSA. A care plan will be developed for the monitoring andtreatment of the at-risk patient. No change is made in the care if ahigh-risk patient.

The augmented plan has the benefit of providing basic monitoring of allpatients for pressure ulcers. The additional steps require additionaltime, however, either by adding staff or further burdening the existingstaff. While superior to the recommended care pathway of FIG. 19A, thecare pathway of FIG. 19B requires more resources and still suffers fromthe limitation that a patient must develop a stage-1 ulcer before VSAidentifies the damage.

Various hospitals and care facilities use different numbers of riskcategories, ranging from two categories, low-risk and at-risk, to fouror more categories, adding categories such as “very-high-risk” to thecategories of the example of FIG. 19B. Patients are assigned to thevarious categories based on the results of the initial risk assessment.

FIG. 20 is an example flowchart of how an apparatus of for assessingperfusion of blood in tissue below a patient's skin may be used in astand-alone process to prevent pressure ulcers, in accordance with thepresent disclosure. Every incoming patient receives a complete perfusionassessment of all body locations that are selected for monitoring. Theseselected locations may include areas recommended in the Instructions ForUse (IFU) of the perfusion measurement apparatus, such as the sacrum andthe heels. Additional locations may be identified by the hospital andintegrated into their in-house practice. Multiple perfusion measurementsare taken at and around each body location at positions that areseparated from each other, although this is generally referred to astaking multiple measurements at the body location. The perfusionmeasurement apparatus calculates a “delta” value for each location fromthe set of measurements taken at and around that location. The deltavalue is then compared to one or more threshold values to categorize apatient. In this example, the patient is assigned to one of two riskcategories: low-risk and at-risk.

In an aspect, the clinician will take perfusion measurements of a bodylocation identified as having possible damage in the initial set ofperfusion measurements at a first time interval. The clinician will alsotake perfusion measurements of all other body locations selected formonitoring at a second time interval that is longer than the first timeinterval. In an aspect, the values of the first and second timeintervals are different depending on the risk category to which thepatient has been assigned. For example, a high-risk patient will have afirst time interval of 4 hours and a second time interval of 1 day whilean at-risk patient will have a first time interval of 1 day and a secondtime interval of 1 week. In an aspect, the time interval may beevent-based, for example upon a change of attending staff or shiftchange, rather than strictly based on time. In general, body locationsthat have elevated delta values are scanned more often than other bodylocations that are monitored but having normal delta values in previousperfusion measurements.

In an aspect, the interval at which perfusion measurements are performedis determined by the delta values from the prior perfusion measurements.For example, a perfusion measurement of a body location that had a deltavalue greater than or equal to a first threshold in a previous perfusionscan is performed at a first time interval, while a perfusionmeasurement is performed at a second time interval that is shorter thanthe first time interval when the prior perfusion measurement of a bodylocation had a delta value greater than or equal to a second thresholdthat is higher than the first threshold.

In this example, low-risk patients receive a weekly perfusion scan ofall body locations that are selected for monitoring. This is a smalleffort that provides basic protection for even the healthiest patients,as a weekly perfusion scan is likely to detect tissue damage before itbecomes visible to VSA.

At-risk patients, which will include patients that would be identifiedas high-risk in the current care pathways of FIGS. 19A and 19B, willreceive specialized care based on the body location that exhibits adelta value above a threshold. For example, if the sacrum body locationhas a delta value above a threshold, the patient will be repositionedevery 6 hours and receive perfusion measurements of the sacrum every dayand perfusion measurements of the other body locations every week.

FIG. 21 is an example flowchart of how an apparatus of for assessingperfusion of blood in tissue below a patient's skin may be used as anadjunct to further improve the augmented treatment decision pathway ofFIG. 19B, in accordance with the present disclosure. An incoming patientreceives both a risk assessment and a perfusion scan of all bodylocations identified by the hospital for monitoring and the assignmentof a patient to a risk category is based partially on the riskassessment and partially on the perfusion scan results. An initial deltavalue that is greater than a threshold is an indication that there ispossible damage at that body location. In an aspect, the assignment isbased solely on the largest initial delta value found during the initialperfusion scan.

A decision whether to implement an intervention, for example turning thepatient at a first interval, is currently based on the VSA and riskassessment despite the uncertainty of whether there is early stagedamage below the skin. In an aspect, the decision to implement anintervention for a particular body site, or a general intervention suchas a high-spec mattress, is based on the delta value found for that sitein the perfusion scan. If the delta value is less than a predeterminedthreshold, no intervention is required. If the delta value is greaterthan the predetermined threshold, then an intervention is selected andimplemented based partially on the body location and partially on thedelta value for that body location. The predetermined threshold forwhether or not to select and implement an intervention may be higher orlower than the threshold for determination that there is possible damageat the body location.

A comparison of the costs of provided the care pathways of FIGS. 19A,19B, 20, and 21 reveals one of the benefits of utilizing a perfusionmeasurement apparatus to monitor patients. Note that the costs citedherein are for patients who do not have or develop pressure ulcers, inwhich case the estimated treatment cost jumps to $2000 for a stage-1ulcer.

The baseline for this comparison is the augmented current practice ofFIG. 19B, which represents a current “best practice” for hospitalsstriving to reduce the incidence rate of pressure ulcers. Providing thecare of the low-risk care pathway is expected to cost an average of $26per patient for the average hospital stay of 5.6 days, the care for anat-risk patient is estimated to cost an average of $121, and a high-riskpatient is expected to cost $165. All of the care pathways rely on a VSAto detect a pressure ulcer and are otherwise implementing interventionsbased on “typical” patient progression rather than the particularpatient's condition.

Integrating a perfusion measurement apparatus into the current “bestpractice” workflow, as shown in FIG. 21 , does not lower the cost of anyof the care pathways as no work element is being eliminated. The benefitis in the ability to detect tissue damage at an earlier stage at aminimal incremental cost. The incremental cost of adding a perfusionscan to the no-risk care pathway is $2, raising the cost fromapproximately $26 to $28. The expected cost of caring for an at-riskpatient who does not have any elevated perfusion delta values, i.e. doesnot have subepidermal tissue damage, is also increased by only $2. If anat-risk patient is found to have an elevated perfusion delta value,however, the patient is escalated to the high-risk category, where theexpected cost of care increases from $165 to $169. While this may seemlike a small additional cost at first glance, it represents an increasein the level of protection provided to at-risk patients.

FIG. 20 represents an example workflow that relies solely on a perfusionmeasurement apparatus to monitor patients and forgoes the routine VSA.The expected cost of preventative care for a low-risk patient is $4,compared to the $28 cost for the integrated low-risk care pathway ofFIG. 21 . For an at-risk patient, which is the only other category forthe perfusion measurement apparatus care pathway of FIG. 20 , theexpected cost is $97, compared to the $123-$169 costs for the at-riskand high-risk patients of the integrated care pathway of FIG. 21 .

Example 9: Perfusion Delta Trends in Heels of Patients is Indicative ofPressure Ulcer Onset

Perfusion measurements are taken over time at the heels of patientsusing an apparatus according to the present disclosure, prior to anyvisual diagnosis of pressure ulcers at the heel. At each time point,each of the patients is directed to have toes pointed away from the bodyand rotated outwards toward the lateral side of the body. A receiver ofthe perfusion detection apparatus is placed on the medial side of theheel. The receiver is adjusted for full contact with the heel, andmultiple measurements are taken around the back of the heel in a curve.Each of the reflected light measurements is converted to a perfusiondelta value by subtracting from the measurement a reference perfusionvalue obtained from another body part of the same patient that is notexperiencing external pressure or mechanical forces. The resultingperfusion delta values in a single day are averaged and plotted for eachpatient.

FIG. 28 illustrates trends of perfusion delta values for seven (7)patients prior to a pressure ulcer diagnosis at one or both of theirheels. Trends across different patients are time-shifted to align to Day0 as the pressure ulcer diagnosis event. A reference perfusion deltacurve (“AVERAGE-H”) is generated by averaging the perfusion delta valuestrends of all patients (n=20) that are eventually visually diagnosedwith a heel pressure ulcer. As shown in FIG. 28 , the perfusion deltavalues of these seven patients exhibit a spike in magnitude two (−2) tofour (−4) days prior to the visual diagnosis compared to the referencecurve. For these patients, a steeper slope of the perfusion delta valuetrend compared to the reference curve is indicative of early onset of apressure ulcer before any visual detection.

Example 10: Intervention Levels Based on Oxygenation Measurements

Subjects identified as being at risk for pressure ulcers are treated inaccordance with the following scheme:

TABLE 3 EXAMPLE INTERVENTION SCHEME FOR TREATING A PATIENT AT RISK FORPRESSURE ULCER Risk Frequency of Subsequent Corresponding LevelIntervention Oxygenation Monitoring SpO₂ Ranges 0 provide goodnutrition, standard every 24 hours SpO₂ ≥ 95% mattress, and/or turnevery 24 hours 1 provide a heel boot; apply dressing to every 4 hours85% ≤ SpO₂ < back or sides of anatomic sites at 95% risk; change ofsupport surfaces; turn patient at a shorter interval 2 provide alow-friction padded every 1 hour SpO₂ < 85% mattress surface; keeppatient's body dry; turn every 1-2 hours

From the foregoing, it will be appreciated that the present inventioncan be embodied in various ways, which include but are not limited tothe following:

Embodiment 1. An apparatus for assessing perfusion of blood in tissuebelow a patient's skin, comprising: an emitter configured to emit lightat a first wavelength and a second wavelength when activated, a firstreceiver configured to measure a first intensity of received light atthe first wavelength and a second intensity of received light at thesecond wavelength and provide a first signal comprising informationabout the first and second intensities of the received light, asubstrate coupled to the emitter and the first receiver and configuredsuch that the emitter and first receiver can be placed in simultaneouscontact with the patient's skin, and a processor coupled to the firstreceiver and configured to: receive the first signal, determine a firstsummation value of the first and second intensities of the receivedlight, and determine a level of perfusion of the tissue from the firstsummation value.

Embodiment 2. The apparatus of embodiment 1, wherein the first receiveris spaced apart from the emitter by a first distance selected so thatthe light emitted by the emitter and received by the first receiver isreflected from a first depth below the patient's skin.

Embodiment 3. The apparatus of embodiment 1 or 2, further comprising asecond receiver, wherein: the second receiver is spaced apart from theemitter by a second distance selected so that the light emitted by theemitter and received by the second receiver is reflected from a seconddepth below the patient's skin, the second receiver is configured to:measure a third intensity of received light at the first wavelength,measure a fourth intensity of received light at the second wavelength,and provide a second signal comprising information about the third andfourth intensities of the received light, and the processor is coupledto the second receiver and configured to: receive the second signal,determine a fifth intensity of the received light by subtracting thethird intensity from the first intensity, determine a sixth intensity ofthe received light by subtracting the fourth intensity from the secondintensity, determine a second summation value of the fifth and sixthintensities, and determine a level of perfusion of the tissue betweenthe first depth and the second depth based on the second summationvalue.

Embodiment 4. The apparatus of any one of embodiments 1 to 3, whereinthe first wavelength is associated with a peak absorption wavelength ofoxygenated hemoglobin and the second wavelength is associated with apeak absorption wavelength of de-oxygenated hemoglobin.

Embodiment 5. The apparatus of any one of embodiments 1 to 4, whereinthe emitter comprises a first source that emits light at the firstwavelength and a second source that emits light at the secondwavelength.

Embodiment 6. The apparatus of embodiment 5, wherein the first sourceand second source can be individually activated.

Embodiment 7. The apparatus of any one of embodiments 1 to 6, whereinthe receiver comprises a first detector that senses light at the firstwavelength and a second detector that senses light at the secondwavelength.

Embodiment 8. The apparatus of embodiment 7, wherein: the processor isindividually coupled to each of the first detector and the seconddetector, and the first signal comprises individual signals from thefirst and second detectors.

Embodiment 9. The apparatus of any one of embodiments 1 to 8, wherein:the processor is coupled to the emitter, the emitter is configured toemit light upon receipt of a strobe pulse, the processor is configuredto provide the strobe pulse to the emitter and to the first receiver,the first receiver is further configured to measure a first time periodbetween receipt of the strobe pulse and receipt of light from theemitter, and the first signal comprises information about the first timeperiod.

Embodiment 10. The apparatus of any one of embodiments 1 to 9, furthercomprising a memory coupled to the processor, wherein the processor isconfigured to store in the memory a series of summation valuesassociated with sequential activations of the emitter.

Embodiment 11. The apparatus of embodiment 10, wherein the processor isfurther configured to determine a range between a smallest summationvalue and a largest summation value of the series of summation values.

Embodiment 12. The apparatus of embodiment 10, wherein the processor isfurther configured to determine a percentage value for each summationvalue relative to a largest summation value in the series of summationvalues.

Embodiment 13. The apparatus of any one of embodiments 1 to 12, furthercomprising an accelerometer that is configured to provide a third signalcomprising information regarding the acceleration of the apparatus inthree spatial dimensions, wherein: the processor is coupled to theaccelerometer and configured to receive the third signal, and theprocessor is further configured to determine a spatial position of theemitter when the emitter is activated.

Embodiment 14. A method of assessing perfusion of blood in tissue belowa patient's skin, the method comprising the steps of: emitting lightinto the patient's skin at a first location on the patient's skin, thelight comprising a first wavelength and a second wavelength, receiving aportion of the emitted light that has been reflected from the tissue,measuring a first intensity of received light at the first wavelengthand a second intensity of received light at the second wavelength,determining a first summation value of the first and second intensitiesof the received light.

Embodiment 15. The method of embodiment 14, further comprising the stepsof: repeating the steps of emitting light, receiving a portion of theemitted light, and measuring the first and second intensities of thereceived light at a second location on the patient's skin, determining asecond summation value of the first and second intensities of thereceived light associated with the second location, and determining adelta value between the first summation value and the second summationvalue.

Embodiment 16. The method of embodiment 14, further comprising the stepsof: repeating the steps of emitting light, receiving a portion of theemitted light, and measuring the first and second intensities of thereceived light at a plurality of locations on the patient's skin,determining a plurality of summation values of the first and secondintensities of the received light associated with the respectiveplurality of locations, identifying a largest summation value from theplurality of summation values, and determining a delta value between thelargest summation value and at least one of the plurality of summationvalues.

Embodiment 17. An apparatus for assessing perfusion of blood in tissuebelow a patient's skin, comprising: an emitter configured to selectablyemit light at a first wavelength or emit light at a second wavelength, acamera configured to form a first image of reflected light at the firstwavelength and a second image of reflected light at the secondwavelength, a substrate coupled to the emitter and the camera andconfigured such that substrate can be placed such that the light emittedby the emitter illuminates a portion of the skin of the patient that iswithin a field of view of the camera, a display, and a processor coupledto the camera and the display and configured to: receive the first andsecond images, form a third image that is a summation of the first andsecond images, and provide the third image on the display.

Embodiment 18. The apparatus of embodiment 17, wherein: the processor iscoupled to the emitter, the processor is further configured to cause theemitter to emit only light at the first wavelength at a first time andemit only light at the second wavelength at a second time, and thecamera forms the first image at the first time and forms the secondimage at the second time.

Embodiment 19. A method of identifying and treating a patient in need ofwound treatment, the method comprising the steps of: evaluating apatient for a risk of tissue damage in a patient upon admission to acare facility, where the evaluating comprises making a first pluralityof perfusion measurements in the patient, calculating a first deltavalue from a portion of the first plurality of perfusion measurements,determining whether the first delta value exceeds a first threshold,administering a first intervention of level-0 if the first delta valuedoes not exceed the first threshold, and administering a firstintervention of level-N if the first delta value exceeds the firstthreshold, where N is an integer and N has a value of 1 or greater.

Embodiment 20. The method of embodiment 19, where the step of making afirst plurality of perfusion measurements comprises using a perfusionmeasurement apparatus to make each perfusion measurement and produce arespective perfusion value, and the step of calculating the first deltavalue comprises comparing the perfusion values produced by a portion ofthe first plurality of perfusion measurements.

Embodiment 21. The method of embodiment 19, where the step of making afirst plurality of perfusion measurements comprises making a firstsub-set of perfusion measurements at the first location and at least oneadditional sub-set of perfusion measurements at a second location, thestep of calculating a first delta value comprises calculating afirst-location first delta value from a portion of the first sub-set ofmeasurements and calculating a second-location first delta value from aportion of the second sub-set of measurements, the step of determiningwhether the first delta value exceeds a first threshold comprisesdetermining whether the first-location first delta value exceeds afirst-location first threshold and determining whether thesecond-location first delta value exceeds a second-location firstthreshold, the step of administering a first intervention of level-0comprises administering a first-location-specific level-0 interventionif the first-location first delta does not exceed the first-locationfirst threshold and administering a second-location-specific level-0intervention if the second-location first delta does not exceed thesecond-location first threshold, and the step of administering a firstintervention of level-N comprises administering afirst-location-specific level-N intervention if the first-location firstdelta exceeds the first-location first threshold and administering asecond-location-specific level-N intervention if the second-locationfirst delta exceeds the second-location first threshold.

Embodiment 22. The method of embodiment 19, where the evaluating stepfurther comprises performing a visual assessment.

Embodiment 23. The method of embodiment 22, where the patient has novisible symptom of a wound.

Embodiment 24. The method of embodiment 19, where the evaluating stepfurther comprises performing a risk assessment.

Embodiment 25. The method of embodiment 19, where N has a value equal to1.

Embodiment 26. The method of embodiment 19, where the value of N is 2 orgreater based on an amount by which the first delta value exceeds thefirst threshold.

Embodiment 27. The method of embodiment 19, where N has a value notexceeding 10.

Embodiment 28. The method of embodiment 19, where the first interventionof level-N is an intervention that is more intensive than the firstintervention of level-0.

Embodiment 29. The method of embodiment 19, further comprising the stepsof: making a second plurality of perfusion measurements in the patientat a first pre-determined frequency corresponding to the administeredintervention level, calculating a second delta value from a portion ofthe second plurality of perfusion measurements, determining whether thesecond delta value exceeds a second threshold, continuing to administerthe first intervention if the second delta value does not exceed thesecond threshold, continuing to make a plurality of perfusionmeasurements at the first pre-determined frequency if the second deltavalue does not exceed the second threshold, administering a secondintervention of level-M if the second delta value exceeds the secondthreshold, where M is an integer and M is greater than N, and making aplurality of perfusion measurements at a second pre-determined frequencycorresponding to level-M if the second delta value exceeds the secondthreshold.

Embodiment 30. The method of embodiment 29, where the second thresholdis the same as the first threshold.

Embodiment 31. The method of embodiment 29, where the second thresholdis greater than the first threshold.

Embodiment 32. The method of embodiment 29, where M has a value equal toN+1, but not exceeding 10.

Embodiment 33. The method of embodiment 29, where the value of M isproportional to an amount by which the second delta value exceeds thesecond threshold.

Embodiment 34. The method of embodiment 29, further comprising the stepsof: determining whether the second delta value is less than a thirdthreshold, administering a level-(N−1) intervention if the second deltavalue is less than the third threshold and if the first intervention isnot of level-0, and making a plurality of perfusion measurements at apre-determined frequency corresponding to level-(N−1) if the seconddelta value is less than the third threshold.

Embodiment 35. The method of embodiment 19, where a level-0 interventionis selected from the group consisting of providing good nutrition,standard mattress, turning every 24 hours, and a combination thereof.

Embodiment 36. The method of embodiment 19, where the first delta valueexceeding the first threshold is calculated from the portion of thefirst plurality of perfusion measurements taken at the patient's heel.

Embodiment 37. The method of embodiment 36, where a level-1 interventionis providing a heel boot to the patient.

Embodiment 38. The method of embodiment 36, where a level-2 interventionis changing the patient's support surface.

Embodiment 39. The method of embodiment 36, where a level-3 interventionis applying dressing to the back or sides of patient's heel.

Embodiment 40. The method of embodiment 36, where a level-4 interventionis changing the patient's sheet cover to a low-friction sheet cover.

Embodiment 41. The method of embodiment 36, where a level-5 interventionis providing a low-friction padded mattress surface for the patient'slower leg.

Embodiment 42. The method of embodiment 36, where a level-6 interventionis turning the patient at a shorter interval than currently providedfor.

Embodiment 43. The method of embodiment 36, where a level-7 interventionis applying a barrier cream to the patient's heel.

Embodiment 44. The method of embodiment 36, where a level-8 interventionis applying a neuro-muscular stimulation to the patient's heel.

Embodiment 45. The method of embodiment 36, where a level-9 interventionis applying a topical cream to the patient's heel to enhance perfusion.

Embodiment 46. The method of embodiment 36, where a level-10intervention is providing a silicon pad for the patient's lower leg.

Embodiment 47. The method of embodiment 19, where the first delta valueexceeding the first threshold is calculated from the portion of thefirst plurality of perfusion measurements taken at the patient's sacrum.

Embodiment 48. The method of embodiment 47, where a level-1 interventionis selected from the group consisting of repositioning the patient witha wedge, keeping the patient's sacrum dry, and a combination thereof.

Embodiment 49. The method of embodiment 47, where a level-2 interventionis changing the patient's mattress to a pressure-alleviating mattress.

Embodiment 50. The method of embodiment 47, where a level-3 interventionis applying a dressing over the patient's sacrum.

Embodiment 51. The method of embodiment 47, where a level-4 interventionis changing the patient's mattress to a dynamic mattress.

Embodiment 52. The method of embodiment 47, where a level-5 interventionis applying a barrier cream to the patient's sacrum.

Embodiment 53. The method of embodiment 47, where a level-6 interventionis applying a neuro-muscular stimulation to the patient's sacrum.

Embodiment 54. The method of embodiment 47, where a level-7 interventionis applying a topical cream to the patient's sacrum to enhanceperfusion.

Embodiment 55. The method of embodiment 47, where a level-8 interventionis providing a silicone pad under the patient's body.

Embodiment 56. The method of embodiment 19, where a level-0pre-determined frequency is every 24 hours.

Embodiment 57. The method of embodiment 19, where a level-1pre-determined frequency is every 10 hours.

Embodiment 58. The method of embodiment 19, where a level-2pre-determined frequency is at the beginning of each nursing shift.

Embodiment 59. The method of embodiment 19, where a level-3pre-determined frequency is every 12 hours.

Embodiment 60. The method of embodiment 19, where a level-4pre-determined frequency is every 8 hours.

Embodiment 61. The method of embodiment 19, where a level-5pre-determined frequency is every 6 hours.

Embodiment 62. The method of embodiment 19, where a level-6pre-determined frequency is every 4 hours.

Embodiment 63. The method of embodiment 19, where a level-7pre-determined frequency is every 2 hours.

Embodiment 64. The method of embodiment 19, where a level-8pre-determined frequency is every 1 hour.

Embodiment 65. The method of embodiment 19, where a level-9pre-determined frequency is every 0.5 hour.

Embodiment 66. A method of slowing the progression of skin and tissuedamage in a patient in need thereof, the method comprising the steps of:identifying a current intervention of level-K received by the patient,making a plurality of perfusion measurements in the patient, calculatinga delta value from a portion of the plurality of perfusion measurements,determining whether the delta value exceeds a first threshold,continuing to administer the current intervention if the delta valuedoes not exceed the first threshold, continuing to make a plurality ofperfusion measurements at a pre-determined frequency corresponding tolevel-K if the delta value does not exceed the first threshold,administering a new intervention of level-N if the delta value exceedsthe first threshold, where N has a value greater than K, and making aplurality of perfusion measurements at a pre-determined frequencycorresponding to level-N if the delta value exceeds the first threshold.

Embodiment 67. The method of embodiment 66, where N has a value equal toK+1, but not exceeding 10.

Embodiment 68. The method of embodiment 66, where the value of N isproportional to an amount by which the delta value exceeds the firstthreshold.

Embodiment 69. The method of embodiment 66, further comprising the stepsof: determining whether the delta value is less than a second threshold,administering a level-L intervention if the delta value is less than thesecond threshold, where L has a non-negative value less than K, andmaking a plurality of perfusion measurements at a pre-determinedfrequency corresponding to level-L if the delta value is less than thesecond threshold.

Embodiment 70. The method of embodiment 69, where L has a value equal toL−1.

Embodiment 71. The method of embodiment 69, where the value of L isselected based on an amount by which the delta value is lower than thesecond threshold.

Embodiment 72. The method of embodiment 66, where the patient in needthereof is a patient experiencing a change of care.

Embodiment 73. The method of embodiment 66, where the patient in needthereof is a patient experiencing a change in mobility.

Embodiment 74. The method of embodiment 66, where the patient in needthereof is a patient experiencing a change in nutrition.

Embodiment 75. The method of embodiment 66, where the patient in needthereof is a patient experiencing a change in sensory perception.

Embodiment 76. The method of embodiment 66, where the patient in needthereof is a patient developing an open ulcer.

Embodiment 77. The method of embodiment 66, where the patient in needthereof is a patient recovering from an open ulcer.

Embodiment 78. The method of embodiment 66, where the patient in needthereof is a patient receiving surgery.

Embodiment 79. The method of embodiment 66, where the patient receivesspinal analgesics during the surgery.

Embodiment 80. The method of embodiment 78, where the patient receivessacral analgesics during the surgery.

Embodiment 81. The method of embodiment 78, where the surgery has aduration of more than 4 hours.

Embodiment 82. A method of selecting a wound treatment for a patient,the method comprising the steps of: evaluating a patient for a risk oftissue damage in a patient upon admission to a care facility, where theevaluating step comprises making a first plurality of perfusionmeasurements in the patient, calculating a first delta value from aportion of the first plurality of perfusion measurements, determiningwhether the first delta value exceeds a first threshold, administering afirst intervention of level-0 if the first delta value does not exceedthe first threshold, and administering a first intervention of level-Nif the first delta value exceeds the first threshold, where N is aninteger and N has a value of 1 or greater.

Embodiment 83. A method of stratifying groups of patients in a carefacility based on risk of wound development, the method comprising thesteps of: making a plurality of perfusion measurements in each of thepatients, calculating a delta value from a portion of the plurality ofperfusion measurements for each of the patients, determining whethereach delta value exceeds any values in a set of threshold valuescorresponding to N care levels and assigning a care level to each of thepatients, rearranging the group of patients based on each of thepatient's assigned care levels.

Embodiment 84. A method of reducing incidence of wound development inpatients admitted to a care facility, the method comprising the stepsof: evaluating a patient for a risk of tissue damage upon admission tothe care facility, where the evaluating step comprises making a firstplurality of perfusion measurements in the patient, calculating a firstdelta value from a portion of the first plurality of perfusionmeasurements, determining whether the first delta value exceeds a firstthreshold, administering a first intervention of level-0 if the firstdelta value does not exceed the first threshold, and administering afirst intervention of level-N if the first delta value exceeds the firstthreshold, where N is an integer and N has a value of 1 or greater.

Embodiment 85. The method of embodiment 84, where the incidence of wounddevelopment in patients in the care facility is reduced to 1 in 100.

Embodiment 86. A method of identifying and treating a patient in need ofapplication of a barrier cream to the patient's heel, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's heel, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a barrier cream to the patient's heel if thedelta value exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.

Embodiment 87. A method of identifying and treating a patient in need ofapplication of a neuro-muscular stimulation to the patient's heel, themethod comprising the steps of: making a plurality of perfusionmeasurements at the patient's heel, calculating a delta value from aportion of the plurality of perfusion measurements, determining whetherthe delta value exceeds a threshold corresponding to level N, where N isgreater than or equal to 2, administering a neuro-muscular stimulationto the patient's heel if the delta value exceeds the threshold, andmaking a plurality of perfusion measurements every hour if the deltavalue exceeds the threshold.

Embodiment 88. A method of identifying and treating a patient in need ofapplication of a topical cream to the patient's heel, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's heel, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a topical cream to the patient's heel if thedelta value exceeds the threshold, and making a plurality of perfusionmeasurements every half an hour if the delta value exceeds thethreshold.

Embodiment 89. A method of identifying and treating a patient in need ofapplication of a barrier cream to the patient's sacrum, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's sacrum, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a barrier cream to the patient's sacrum if thedelta value exceeds the threshold, and making a plurality of perfusionmeasurements every six hours if the delta value exceeds the threshold.

Embodiment 90. A method of identifying and treating a patient in need ofapplication of a neuro-muscular stimulation to the patient's sacrum, themethod comprising the steps of: making a plurality of perfusionmeasurements at the patient's sacrum, calculating a delta value from aportion of the plurality of perfusion measurements, determining whetherthe delta value exceeds a threshold corresponding to level N, where N isgreater than or equal to 2, administering a neuro-muscular stimulationto the patient's sacrum if the delta value exceeds the threshold, andmaking a plurality of perfusion measurements every four hours if thedelta value exceeds the threshold.

Embodiment 91. A method of identifying and treating a patient in need ofapplication of a topical cream to the patient's sacrum, the methodcomprising the steps of: making a plurality of perfusion measurements atthe patient's sacrum, calculating a delta value from a portion of theplurality of perfusion measurements, determining whether the delta valueexceeds a threshold corresponding to level N, where N is greater than orequal to 2, administering a topical cream to the patient's sacrum if thedelta value exceeds the threshold, and making a plurality of perfusionmeasurements every two hours if the delta value exceeds the threshold.

Embodiment 92. An apparatus for identifying damaged tissue, theapparatus comprising: an emitter and two receivers, where each of theemitter and two receivers is configured to be placed against a patient'sskin, a processor electronically coupled to the receivers and configuredto receive the information from a receiver and convert the informationinto a perfusion value, and a non-transitory computer-readable mediumelectronically coupled to the processor and comprising instructionsstored thereon that, when executed on the processor, perform the stepof: determining a difference between a first perfusion valuecorresponding to reflected light as measured by the first receiver at afirst location on the patient's skin and a second perfusion valuecorresponding to reflected light as measured by the second receiver at asecond location on the patient's skin, where the second location isbisymmetric relative to the first location.

Embodiment 93. The apparatus according to embodiment 92, where thedifference being greater than a predetermined threshold is indicative ofdamaged tissue at one of the first and second locations.

Embodiment 94. The apparatus according to embodiment 93, furthercomprising: a substrate configured to be placed in a known position onthe patient's skin, and the first and second receivers are disposed onthe substrate such that the first and second receivers are positioned atbisymmetric locations on the patient's skin when the substrate is placedin the known position on the patient's skin.

Embodiment 95. The apparatus according to embodiment 92, furthercomprising a gap between the first and second receivers.

Embodiment 96. An apparatus for identifying damaged tissue, theapparatus comprising: a substrate configured to be placed against asurface of a patient's skin, a plurality of emitters that are disposedon the substrate at a respective plurality of positions and a pluralityof receivers that are disposed on the substrate at a respectiveplurality of positions, where each receiver is configured to measure thereflected light and provide information regarding blood perfusion, aprocessor electronically coupled to the receivers and configured toreceive the information regarding reflected light and convert theplurality of reflected light measurements into a respective plurality ofperfusion values, and a non-transitory computer-readable mediumelectronically coupled to the processor and comprising instructionsstored thereon that, when executed on the processor, perform the stepsof: identifying from the plurality values a first receiver and a secondreceiver that are located at first and second positions that arebisymmetric with respect to the patient's skin, and comparing a firstperfusion value that is associated with the first receiver with a secondperfusion value that is associated with the second receiver.

Embodiment 97. The apparatus according to embodiment 96, where theinstructions further comprise the steps of: determining a differencebetween the first and second perfusion values, and providing anindication that tissue is damaged at one of the first and secondlocations if the difference is greater than a predetermined threshold.

Embodiment 98. The apparatus according to embodiment 96, where theinstructions further comprise the steps of: determining a differencebetween the first and second perfusion values, determining which of thefirst and second perfusion values is larger than the other, andproviding an indication that tissue is damaged at the locationassociated with the larger perfusion value if the difference is greaterthan a predetermined threshold.

Embodiment 99. An apparatus for identifying damaged tissue, theapparatus comprising: an apparatus body; an emitter; a first receiverand a second receiver, where the two receivers are disposed on theapparatus body to allow simultaneous positioning of the first receiveron a first location on a patient's skin and the second receiver on asecond location bisymmetric relative to the first location; a circuitelectronically coupled to each of the two receivers and configured tomeasure the reflected light detected by each of the two receivers; aprocessor electronically coupled to the circuit that is configured toreceive a first reflected light measurement from a first location and asecond reflected light measurement from a second location, and toconvert the first reflected light measurement to a first perfusion valueand the second reflected light measurement to a second perfusion value;a non-transitory computer-readable medium electronically coupled to theprocessor and contains instructions that, when executed on theprocessor, perform the step of determining a difference between thefirst perfusion value and the second perfusion value.

Embodiment 100. The apparatus according to embodiment 99, where each ofthe two receivers are disposed on two ends of the apparatus body whilebeing aligned on a common plane.

Embodiment 101. The apparatus according to embodiment 99, where theapparatus body is rigid and maintains the two receivers at a fixedseparation distance and fixed orientation to each other.

Embodiment 102. The apparatus according to embodiment 99, where theapparatus body is flexible and allows the two receivers to be orientedat an angle to each other.

Embodiment 103. The apparatus according to embodiment 102, where theapparatus body comprises a hinge.

Embodiment 104. The apparatus according to embodiment 99, where thefirst reflected light measurement and the second reflected lightmeasurement are measured simultaneously.

Embodiment 105. The apparatus according to embodiment 104, where theapparatus further comprises a contact sensor positioned proximate to oneof the two receivers, and where the simultaneous measurements aretriggered by the actuation of the contact sensor.

Embodiment 106. The apparatus according to embodiment 105, where thecontact sensor is a pressure sensor or an optical sensor.

Embodiment 107. The apparatus according to embodiment 99, where theinstructions further comprise the step of providing an indication thattissue is damaged at one of the first and second locations if thedifference is greater than a predetermined threshold.

Embodiment 108. The apparatus according to embodiment 99, where theinstructions further comprise the steps of: determining the greater ofthe first and second perfusion values, and providing an indication thattissue is damaged at the location associated with the greater perfusionvalue if the difference exceeds a predetermined threshold.

Embodiment 109. A method for identifying damaged tissue, the methodcomprising: obtaining a first perfusion value from a first location on apatient's skin; obtaining a second perfusion value from a secondlocation that is bisymmetric relative to the first location; determininga difference between the first perfusion value and the second perfusionvalue.

Embodiment 110. The method according to embodiment 109, furthercomprising providing an indication that tissue is damaged at one of thefirst and second locations if the difference is greater than apredetermined threshold.

Embodiment 111. The method according to embodiment 109, furthercomprising: determining the greater of the first and second perfusionvalues, and providing an indication that tissue is damaged at thelocation associated with the greater perfusion value if the differenceexceeds a predetermined threshold.

Embodiment 112. A method of detecting tissue damage before it is visibleon a patient's skin, comprising: measuring a plurality of perfusionvalues at a single location at incremental times, calculating a slopebetween the latest perfusion value and the immediately prior perfusionvalue, comparing this slope to a threshold value, and determining thatthere is tissue damage if the slope exceeds the threshold value.

Embodiment 113. A method of detecting tissue damage before it is visibleon a patient's skin, comprising: measuring a plurality perfusion valuesat a plurality of locations at incremental times, calculating a deltavalue for the plurality of perfusion values for each time, calculating aslope between the latest delta value and the immediately prior deltavalue, comparing this slope to a threshold value, and determining thatthere is tissue damage if the slope exceeds the threshold value.

Embodiment 114. A method of detecting tissue damage before it is visibleon a patient's skin, comprising: measuring a plurality of perfusionvalues at a single location at each of a plurality of incremental times,calculating a perfusion delta value for each incremental time, fitting acurve to a predetermined number of the most-recent perfusion deltavalues, calculating a curvature of the fitted curve, comparing thiscurvature to a threshold value, and determining that there is tissuedamage if the curvature exceeds the threshold value.

While the invention has been described with reference to particularaspects, it will be understood by those skilled in the art that variouschanges may be made and equivalents may be substituted for elementsthereof without departing from the scope of the invention. In addition,many modifications may be made to a particular situation or material tothe teachings of the invention without departing from the scope of theinvention. Therefore, it is intended that the invention not be limitedto the particular aspects disclosed but that the invention will includeall aspects falling within the scope and spirit of the appended claims.

We claim:
 1. An apparatus for assessing blood perfusion, said apparatuscomprising: an emitter configured to emit light at a first wavelengthand a second wavelength when activated, a first receiver and a secondreceiver, wherein said first receiver is configured to be placed at afirst location on a patient's skin and said second receiver isconfigured to be placed at the same time against a second location onsaid patient's skin, wherein said second location is bisymmetricrelative to said first location, a circuit electronically coupled tosaid first receiver and said second receiver and configured to measure afirst reflected light property of said first receiver and to measure asecond reflected light property of said second receiver and provideinformation regarding said first and second reflected light properties,a processor electronically coupled to said circuit and configured toreceive said information, and a non-transitory computer-readable mediumelectronically coupled to said processor and comprising instructionsstored thereon that, when executed on said processor, perform the stepsof: converting said first reflected light property into a firstperfusion value and said second reflected light property into a secondperfusion value, and determining a difference between said firstperfusion value and said second perfusion value.
 2. The apparatusaccording to claim 1, wherein said instructions further comprise a stepof providing a signal if said difference is greater than a predeterminedthreshold.
 3. The apparatus according to claim 1, further comprising aswitching element configured to detect when said first and secondreceivers are in proper contact with said patient's skin wherein: saidcircuit is electronically coupled to said switching element andconfigured to measure said first and second reflected light propertieswhen said first and second receivers are in proper contact with saidpatient's skin.
 4. The apparatus according to claim 2, furthercomprising: a substrate configured to be placed in a known position onsaid patient's skin, and said first and second receivers are disposed onsaid substrate such that said first and second receivers are positionedat bisymmetric locations on said patient's skin when said substrate isplaced in said known position on said patient's skin.
 5. An apparatusfor assessing blood perfusion, said apparatus comprising: an apparatusbody; an emitter configured to emit light at a first wavelength and asecond wavelength when activated; a first receiver and a secondreceiver, wherein said two receivers are disposed on said apparatus bodyto allow simultaneous positioning of said first receiver on a firstlocation on a patient's skin and said second receiver on a secondlocation bisymmetric relative to said first location; a circuitelectronically coupled to each of said two receivers and configured tomeasure reflected light detected by each of said two receivers; aprocessor electronically coupled to said circuit and is configured toreceive a first reflected light measurement from a first location and asecond reflected light measurement from a second location, and toconvert said first reflected light measurement to a first perfusionvalue and said second reflected light measurement to a second perfusionvalue; and a non-transitory computer-readable medium electronicallycoupled to said processor and contains instructions that, when executedon said processor, perform the step of determining a difference betweensaid first perfusion value and said second perfusion value.
 6. Theapparatus according to claim 5, wherein each of said two receivers aredisposed on two ends of said apparatus body while being aligned on acommon plane.
 7. The apparatus according to claim 5, wherein saidapparatus body is rigid and maintains said two receivers at a fixedseparation distance and fixed orientation to each other.
 8. Theapparatus according to claim 5, wherein said apparatus body is flexibleand allow said two receivers to be oriented at an angle to each other.9. The apparatus according to claim 8, wherein said apparatus bodycomprises a hinge.
 10. The apparatus according to claim 5, wherein saidfirst reflected light measurement and said second reflected lightmeasurement are measured simultaneously.
 11. The apparatus according toclaim 10, wherein said apparatus further comprises a contact sensorpositioned proximate to one of said two receivers, and wherein saidsimultaneous measurements are triggered by the actuation of said contactsensor.
 12. The apparatus according to claim 11, wherein said contactsensor is a pressure sensor or an optical sensor.
 13. The apparatusaccording to claim 5, wherein said instructions further comprise thestep of providing an indication that tissue is damaged at one of saidfirst and second locations if the difference is greater than apredetermined threshold.
 14. The apparatus according to claim 5, whereinsaid instructions further comprise the steps of: determining the greaterof said first and second perfusion values, and providing an indicationthat tissue is damaged at the location associated with the greaterperfusion value if the difference exceeds a predetermined threshold. 15.An apparatus for assessing perfusion of blood in tissue below apatient's skin, comprising: an emitter configured to emit light at afirst wavelength and a second wavelength when activated, wherein theemitter comprises a first source that emits light at the firstwavelength and a second source that emits light at the secondwavelength, a first receiver configured to measure a first intensity ofreceived light at the first wavelength and a second intensity ofreceived light at the second wavelength and provide a first signalcomprising information about the first and second intensities of thereceived light, wherein the first receiver comprises a first detectorthat senses light at the first wavelength and a second detector thatsenses light at the second wavelength, a substrate coupled to theemitter and the first receiver and configured such that the emitter andfirst receiver can be placed in simultaneous contact with the patient'sskin, and a processor coupled to each of the first detector and thesecond detector of the first receiver and configured to: receive thefirst signal, wherein the first signal comprises individual signals fromthe first and second detector, determine a first summation value of thefirst and second intensities of the received light, and determine alevel of perfusion of the tissue from the first summation value.
 16. Anapparatus for assessing perfusion of blood in tissue below a patient'sskin, comprising: an emitter configured to emit light at a firstwavelength and a second wavelength when activated, a first receiverconfigured to measure a first intensity of received light at the firstwavelength and a second intensity of received light at the secondwavelength and provide a first signal comprising information about thefirst and second intensities of the received light, a substrate coupledto the emitter and the first receiver and configured such that theemitter and first receiver can be placed in simultaneous contact withthe patient's skin, and a processor coupled to the first receiver andconfigured to: receive the first signal, determine a first summationvalue of the first and second intensities of the received light, anddetermine a level of perfusion of the tissue from the first summationvalue, wherein: the processor is coupled to the emitter, the emitter isconfigured to emit light upon receipt of a strobe pulse, the processoris configured to provide the strobe pulse to the emitter and to thefirst receiver, the first receiver is further configured to measure afirst time period between receipt of the strobe pulse and receipt oflight from the emitter, and the first signal comprises information aboutthe first time period.
 17. An apparatus for assessing blood perfusion,said apparatus comprising: a substrate configured to be placed against asurface of a patient's skin, a plurality of emitters that are disposedon said substrate at a respective plurality of positions, where each ofsaid plurality of emitters is configured to emit light at a firstwavelength and a second wavelength when activated, a plurality ofreceivers that are disposed on said substrate at a respective pluralityof positions, a circuit electronically coupled to said plurality ofreceivers and configured to measure reflected light of a portion of saidplurality of receivers and provide a plurality of information regardingsaid reflected light, a processor electronically coupled to said circuitand configured to receive said plurality of information regarding saidreflected light from said circuit and convert said plurality of saidinformation regarding said reflected light into a respective pluralityof perfusion values, and a non-transitory computer-readable mediumelectronically coupled to said processor and comprising instructionsstored thereon that, when executed on said processor, perform the stepsof: identifying from said plurality of perfusion values a first receiverand a second receiver that are located at first and second positionsthat are bisymmetric with respect to said patient's skin, and comparinga first perfusion value that is associated with said first receiver witha second perfusion value that is associated with said second receiver.18. The apparatus according to claim 17, wherein said instructionsfurther comprise the steps of: determining a difference between saidfirst and second perfusion values, and providing an indication thattissue is damaged at one of said first and second locations if saiddifference is greater than a predetermined threshold.
 19. The apparatusaccording to claim 17, wherein said instructions further comprise thesteps of: determining a difference between said first and secondperfusion values, determining which of said first and second perfusionvalues is larger than the other, and providing an indication that tissueis damaged at the location associated with the larger perfusion value ifsaid difference is greater than a predetermined threshold.